Mirtazapine vs Sertraline for Anxiety (Australia)

When treating anxiety, two commonly prescribed medications are Mirtazapine (brand names Avanza®, Remeron®) and Sertraline (brand name Zoloft®). Both are antidepressants used in managing anxiety disorders, but they differ in how they work, their side effect profiles, how quickly they act, and other factors. This article provides a comprehensive comparison of mirtazapine and sertraline for anxiety treatment, with an Australian context in mind. We’ll cover their mechanisms of action, side effects, onset times, withdrawal symptoms, half-lives, alcohol interactions, available strengths in Australia, use for flight anxiety (e.g. “sleeping pills for flying anxiety”), and ultimately help you understand which might be better for different anxiety profiles. We’ll also address some frequently asked questions. Throughout, we’ll highlight key points (in bold) for clarity and reference authoritative sources for accuracy. (If you’re managing anxiety and considering medication, remember these drugs require a prescription – services like NextClinic’s prescription renewal can help streamline the process.)

Looking for online prescriptions?

Starting from $29.90

Request Now

Looking for online prescriptions?

Starting from $29.90

Request Now

Mechanism of Action: How Each Drug Works for Anxiety

Mirtazapine’s Mechanism: Mirtazapine is an atypical antidepressant (specifically a NaSSA, noradrenergic and specific serotonergic antidepressant). It works by balancing chemicals in the brain that affect mood and anxiety, primarily boosting serotonin and noradrenaline levels. Unlike SSRIs, mirtazapine does not inhibit serotonin reuptake; instead, it blocks certain presynaptic receptors (alpha-2 adrenergic receptors) which leads to increased release of serotonin and norepinephrine. It also blocks specific serotonin receptors (5-HT2 and 5-HT3) and strongly blocks histamine H1 receptors. The net effect is increased serotonin availability (especially at the 5-HT1 receptors linked to anti-anxiety effect) and increased norepinephrine, while the antihistamine action causes sedation. In anxiety treatment, this dual action can help improve mood and reduce tension. Mirtazapine’s sedative effect (from H1 blockade) can be useful for patients with anxiety who have trouble sleeping, as it tends to cause relaxation and drowsiness.

Sertraline’s Mechanism: Sertraline is a selective serotonin reuptake inhibitor (SSRI). It treats anxiety by increasing serotonin levels in the brain – it blocks the reabsorption (reuptake) of serotonin in synapses, making more serotonin available to improve neurotransmission. Serotonin is a neurotransmitter that regulates mood, anxiety, and stress, so having more of it active can alleviate anxiety symptoms. Sertraline’s targeted action on serotonin makes it effective across many anxiety-related conditions (from generalised anxiety to panic and social anxiety). It does not significantly affect other neurotransmitters at typical doses, which is why it’s generally activating or neutral (rather than sedating). Over time (a few weeks of use), the increased serotonin helps to calm excessive fear responses and worry, leading to reduced anxiety. Sertraline is first-line for anxiety disorders in numerous guidelines​ because of this effective mechanism and a well-established evidence base.

In summary, mirtazapine works via multiple pathways (serotonin, norepinephrine, and histamine) which can reduce anxiety and improve sleep, whereas sertraline works by selectively enhancing serotonin which lifts mood and eases anxiety. Both ultimately rebalance brain chemistry to relieve anxiety, but through different pharmacological routes.

Side Effects

All medications have side effects, and it’s important to compare what you might experience on mirtazapine vs sertraline. Each person is different, but we can outline common side effects and serious (less common) side effects for both drugs.

Mirtazapine Side Effects: Because of its antihistamine effect, drowsiness and tiredness are very common on mirtazapine. Many patients feel quite sleepy, especially at lower doses (15–30 mg); this is why mirtazapine is often taken at night. Along with sedation, increased appetite and weight gain are frequently reported. Mirtazapine can make you crave food more (sometimes very carb-rich foods) and it changes metabolism, so weight gain can be an issue with long-term use. Other possible side effects include dry mouth, dizziness, and weakness or fatigue. Some people may have fluid retention (swelling in ankles etc.). On the plus side, mirtazapine tends to cause fewer sexual side effects than SSRIs – it typically does not lower libido or delay orgasm like SSRIs can. Also, it’s less likely to cause the nausea or gut upset that SSRIs sometimes cause; in fact, it can have an anti-emetic (anti-nausea) effect by blocking 5-HT3 receptors (the same ones targeted by some anti-nausea meds).

Rare but serious side effects of mirtazapine include restless agitation (akathisia) or unusual changes in behavior, and in very rare cases, blood cell problems. A very uncommon side effect is agranulocytosis, a drop in white blood cells – this could lead to frequent infections. Because of this, you should report symptoms like unexplained fever, sore throat, or mouth ulcers while on mirtazapine (especially in the first weeks). Another serious risk (common to all antidepressants) is increased suicidal thoughts in some young people – close monitoring is essential during early treatment​. Overall, though, mirtazapine is considered to have a favorable side-effect profile for most patients – sedation and weight gain are the main issues to watch.

Sertraline Side Effects: SSRIs like sertraline have their own set of side effects. Common ones when starting sertraline include nausea, diarrhea or upset stomach, sometimes loss of appetite (opposite to mirtazapine) or mild weight loss initially. Sertraline can also cause insomnia or trouble sleeping for some (it can be mildly activating), though others might feel a bit fatigued or sleepy – it varies. One of the most notorious SSRI side effects involves sexual dysfunction: sertraline often can decrease sex drive, delay ejaculation, or make it harder to reach orgasm. These sexual side effects are usually reversible if the drug is stopped, and sometimes they diminish after a few weeks, but in some cases they persist. Another common effect is increased sweating or feeling sweaty with minimal exertion. You might also experience headache or mild tremors or jitteriness, especially early on. Many people feel a bit “on edge” or restless during the first week or two on sertraline as their body adjusts (initial anxiety may increase before it improves – a known quirk of SSRIs).

For serious side effects, sertraline and other SSRIs carry a risk of serotonin syndrome – a rare but dangerous condition caused by excessive serotonin. This usually only happens if sertraline is combined with other serotonergic drugs (like certain migraine meds or St John’s Wort or MDMA, etc.) and can cause high fever, agitation, muscle stiffness, and confusion. Sertraline can also in rare cases lead to low sodium levels in the blood (hyponatremia), especially in older adults – leading to weakness, confusion, or even seizures. Another uncommon effect is a tendency toward easy bleeding or bruising, because SSRIs can slightly affect platelets (caution if you take NSAIDs or aspirin regularly). As with all antidepressants, monitor for worsening depression or suicidal thoughts, particularly in young adults when first starting.

Comparing the two: In practice, mirtazapine’s side effects often center around sedation and weight gain, whereas sertraline’s focus on gastrointestinal symptoms and sexual side effects. For someone with terrible insomnia and poor appetite, mirtazapine’s profile might actually be beneficial (helps sleep and weight). On the other hand, for someone very concerned about weight gain or daytime sleepiness (e.g. they need to be alert at work), sertraline might be better. It’s worth noting that neither drug is considered addictive, and most side effects are manageable with dose adjustments or tend to subside after a few weeks. Always discuss troubling side effects with your doctor – sometimes switching medication is the best remedy if side effects outweigh benefits.

(Pro tip: If you experience drowsiness on mirtazapine, take it at night before bed. For sertraline-induced nausea, taking it with food in the morning can help. Sexual side effects on sertraline that don’t resolve – talk to your GP; they may adjust the dose or suggest an alternative. And remember, NextClinic’s prescription renewal service can be handy if you and your doctor have found the right med and dose – you can conveniently renew your script when needed.)

Onset Time: How Long Until Each Starts Working?

One of the biggest questions when you start an anxiety medication is: How long before I feel relief? Both mirtazapine and sertraline take time to work, but there are some differences.

Mirtazapine Onset: Mirtazapine is often noted for a relatively faster onset of action compared to many SSRIs. You might notice improved sleep almost immediately (within the first few days) due to its sedative effect. For mood and anxiety symptoms, some improvement can occur in 1–2 weeks, and it often reaches a full therapeutic effect by 4 weeks. In fact, some studies have shown mirtazapine can start reducing anxiety and depression symptoms as early as the first week – one clinical trial specifically comparing mirtazapine and sertraline found a significant improvement with mirtazapine by the 4th day of treatment versus sertraline. This doesn’t mean everyone will feel better in 4 days (that was an average finding in a controlled setting), but it underscores that mirtazapine tends to act quickly. By 2–4 weeks, many patients have substantial relief, and by 6 weeks its full effect should be evident.

Sertraline Onset: Sertraline (like other SSRIs) generally takes a bit longer for the therapeutic effects on anxiety to kick in. Some symptoms (like improvement in sleep or a slight lift in mood) may start in 1–2 weeks, but significant anxiety reduction often takes about 4–6 weeks. It’s common that around week 2 or 3 you might notice subtle changes – perhaps fewer panic attacks or less general worry – but the peak benefit is usually by week 6 to 8 of continuous treatment. It’s important to be patient and keep taking it daily, even if you don’t feel better right away. The delay is due to the time it takes for serotonin levels to adjust and for downstream changes (like receptor sensitivities) to occur in your brain. Interestingly, sometimes anxiety can feel a bit worse initially on sertraline, possibly due to transient increased serotonin – but this usually settles within the first 1–2 weeks. By one month, most people will know if sertraline is helping; if there’s no improvement at all by 6–8 weeks, doctors might consider a dose increase or a different strategy​.

Quick comparison: Mirtazapine often yields faster relief of anxiety/sleep symptoms – you might sleep better within days and see anxiety improvements within 2 weeks, whereas sertraline might require 4–6 weeks for full effect. However, by the 2-month mark, both can be equally effective – it’s the early weeks where mirtazapine has an edge in speed. If you have very severe anxiety and need quicker calming (and can tolerate sedation), mirtazapine might provide relief sooner. If you can afford to wait a bit and want to avoid the sedation/weight issues, sertraline is a proven path (just remember to stick with it through the early phase). Always keep in close touch with your doctor during those first weeks to monitor progress – and don’t give up too soon, since these medications need time to work.

Withdrawal Symptoms: Stopping the Medication

Neither mirtazapine nor sertraline is considered “addictive,” but if you stop them suddenly after a period of regular use, you can experience withdrawal symptoms (also called discontinuation symptoms). This is because your brain needs time to adjust when a medication influencing neurotransmitters is removed.

Mirtazapine Withdrawal: If mirtazapine is discontinued abruptly, some people experience rebound symptoms. According to Australian health guidelines, do not stop mirtazapine suddenly – it can cause nausea, headache, dizziness, and anxiety to flare up. Other reports of mirtazapine withdrawal include irritability, restlessness, insomnia, sweating, and generally feeling unwell (flu-like symptoms). Because mirtazapine has a moderate half-life (~20–40 hours, see next section), these symptoms might start within a couple of days of the last dose and can last 1–2 weeks or more if not addressed. The good news is mirtazapine’s withdrawal tends to be a bit milder than some SSRIs – for example, people usually don’t report the “electric shocks” sensation (brain zaps) that are classic with some other antidepressants. Nonetheless, a gradual tapering plan (reducing the dose over a few weeks) is recommended to minimize any discontinuation effects. If tapered properly (e.g. 30mg down to 15mg for a week or two, then to 7.5mg if possible, then stop), many can come off mirtazapine with minimal discomfort. Always consult your doctor for a taper schedule; they might even provide some short-term support meds if needed to handle symptoms.

Sertraline Withdrawal: Stopping sertraline suddenly can lead to SSRI discontinuation syndrome. This can include dizziness, vertigo, nausea, fatigue, headache, anxiety, irritability, insomnia, and sensory disturbances (those “zaps” or tingling feelings). Patients sometimes describe it like having the flu combined with anxiety and odd nerve sensations. Withdrawal symptoms usually begin within a few days of the last dose (sometimes even within 1–2 days, given sertraline’s ~1 day half-life). The severity can range from mild “I feel a bit off for a week” to quite distressing symptoms in others. Typically, these symptoms last 1-3 weeks and then resolve, but in some cases they can last longer if the sertraline was stopped very abruptly or if the person was on it for a long time. Sertraline is not the worst SSRI for withdrawal – paroxetine and venlafaxine (an SNRI) are known to have more severe withdrawal, whereas fluoxetine (with its long half-life) has the least. Sertraline falls in the middle: it can cause notable withdrawal symptoms if stopped cold turkey, so a gradual taper is advised. For example, if you were on 100mg daily, your doctor might reduce to 50mg for a week or two, then 25mg for another week, before stopping. This allows your brain chemistry to adjust slowly. Following such a taper, many people have either very mild symptoms or none at all.

Avoiding withdrawal: The key with both medications is don’t abruptly stop on your own. Always involve your GP or psychiatrist in making a discontinuation plan. They will tailor a dose reduction schedule based on how long you’ve been on the medication and your current dose. If you do experience withdrawal symptoms, know that it’s usually self-limiting (it will pass with time) and can be managed with supportive care. For instance, if anxiety spikes during withdrawal, a doctor might prescribe a short course of a benzodiazepine or hydroxizine to ease the anxiety until your system stabilizes – but only under supervision, since you don’t want to swap one issue for another. Some people mistakenly think they became “addicted” because they feel unwell when stopping – this is not true addiction (no one craves sertraline or mirtazapine for a high), it’s just the brain readjusting.

Bottom line: Taper off slowly. If done correctly, withdrawal can be minimal. If done abruptly, both drugs can produce a withdrawal syndrome – sertraline’s might include dizziness and sleep disturbance, while mirtazapine’s might include nausea and anxiety. Planning and medical guidance make all the difference. And never be afraid to tell your doctor if you’re struggling to come off – they can help extend the taper or manage symptoms. (Also, if cost or travel makes it hard to see a doctor for this, remember services like NextClinic can assist with managing prescription changes or renewals via telehealth.)

Half-Life: How Long Do They Stay in Your System?

The half-life of a drug is the time it takes for the blood level of the drug to drop to half. It gives an idea of how long the drug’s effects last and how quickly it leaves your body. Half-life also ties into dosing frequency and withdrawal as discussed.

Mirtazapine Half-Life: Mirtazapine’s half-life is around 20 to 40 hours (roughly 0.8–1.6 days). On average, let’s say ~30 hours in many patients. This means once you take a dose, about a day later half of it is still in your system. Usually, a steady state is reached in a week or so of daily dosing. The half-life can be on the shorter end (~20h) in younger individuals and longer (~40h) in older or those with liver issues. Because of this half-life, mirtazapine is dosed once daily (typically at night). It also means that if you miss a single dose, you might not feel too awful, as the drug levels decline gradually. In terms of lingering in your body, mirtazapine would be mostly gone after about 4–8 days (about 5 half-lives for full elimination). The moderate half-life is why withdrawal symptoms can start about 1–2 days after stopping – it’s not ultra-short, but within a couple days levels drop significantly.

Sertraline Half-Life: Sertraline’s half-life is approximately 26 hours (1.1 days). So it’s actually quite similar to mirtazapine. Sertraline, however, has an active metabolite (desmethylsertraline) with a longer half-life (~2–3 days), but that metabolite is much less potent. Sertraline is also a once-daily medication due to this half-life. If you take it every morning, by the next morning levels have gone down by about 50%, but then you take the next dose and keep it in range. Like mirtazapine, if you miss a dose, you might start feeling a bit off by day 2 of missing it (some people sensitive to withdrawals might even feel it late on the first day missed). After stopping completely, sertraline would be mostly eliminated in about a week as well. One big difference: because sertraline’s metabolite sticks around, the tail-off might be slightly smoother than a med like paroxetine (which has a very short half-life). In practice, sertraline’s half-life is long enough to allow once-daily dosing but short enough that withdrawal can occur if stopped suddenly.

Implications of half-life: Both drugs staying in your system ~1 day means they have a consistent daily effect and need daily dosing to maintain steady relief from anxiety. Neither is a “take as needed” situation; you must take them continuously for benefit. The similar half-lives also mean both should be tapered when discontinuing – there isn’t a huge difference here. However, as noted above, some other SSRIs like fluoxetine (Prozac) have a much longer half-life (~5 days, plus an active metabolite for weeks), which is why Prozac can sometimes be used to cross-taper or mitigate withdrawal from shorter half-life SSRIs. For sertraline, sometimes doctors do a strategy of switching to fluoxetine then stopping, to use that long half-life to wean – but this is usually only for very severe withdrawal cases.

For the average person, knowing the half-life mostly helps in understanding dosing schedules and what happens if you miss doses. With both sertraline and mirtazapine, try not to miss doses. If you do forget one, generally don’t double up the next dose; just resume normal schedule. Due to their half-lives, missing one dose might slightly increase anxiety or cause a fleeting symptom (some people report feeling zappy or anxious if they miss an SSRI dose), but most often it’s okay if it’s a one-time miss. If you miss multiple doses, you risk symptom return and some withdrawal.

In summary, mirtazapine (~30h) and sertraline (~26h) have comparable half-lives, facilitating convenient once-daily dosing. Neither stays for extremely long, so they clear out within days after stopping (necessitating careful discontinuation to avoid a sudden drop). This also means after you stop, if you had side effects, they should subside within a few days as the drug leaves your system.

Alcohol Interaction: Can You Drink on Mirtazapine or Sertraline?

Combining alcohol with any antidepressant is generally cautioned against. Alcohol itself affects brain chemistry and can worsen anxiety or depression in the long run. Here’s what to know about drinking while on these meds:

Mirtazapine and Alcohol: Avoid alcohol while taking mirtazapine. This medication can enhance the sedative effects of alcohol, meaning if you drink, you’ll likely feel more intoxicated or sleepy than you normally would. Both mirtazapine and alcohol depress the central nervous system; together, they can impair your coordination and alertness significantly (think: extreme drowsiness, dizziness, risk of falling or blacking out). The Australian consumer info explicitly warns that mirtazapine can make the effects of alcohol stronger. So that one glass of wine might hit like two or three glasses. This not only can be dangerous (for example, driving under the influence becomes even riskier) but also counterproductive – remember, alcohol can actually worsen sleep quality and anxiety later, undermining what the medication is trying to fix. Additionally, heavy alcohol use while on mirtazapine could strain your liver, as both are processed there. If you have a special occasion and want to have a small drink, discuss it with your doctor – they may say one standard drink occasionally is okay if you tolerate mirtazapine well, but caution is key. Many patients on mirtazapine find they either don’t crave alcohol as much (since it improves sleep, they don’t feel the need for a nightcap) or they simply cut it out due to the increased sedation.

Sertraline and Alcohol: With sertraline (and SSRIs in general), the stance is a bit more lenient yet still cautionary. Moderate alcohol consumption is unlikely to cause a dangerous interaction with sertraline, but it may make side effects worse and is not recommended. SSRIs do not cause drowsiness in everyone, but sertraline can cause some people to feel sleepy or less alert – alcohol will amplify any such effect. Moreover, alcohol can counteract the benefit of an antidepressant. The NPS MedicineWise guidance notes that while moderate amounts might not affect your response to sertraline, your doctor may suggest avoiding alcohol altogether while on it. This is partly because alcohol is a depressant – it can make you more depressed or anxious the day after drinking (the hangxiety phenomenon). Also, combining alcohol with an SSRI might increase risks like bleeding in the stomach (if heavy drinking irritates the gut, and SSRIs affect platelets a bit). The UK NHS advises that you can drink on sertraline but it might make you sleepy, so be careful. Essentially, if you decide to have a drink, do so in small amounts first to see how you react. Never drive or operate machinery if you’ve mixed sertraline and alcohol until you know you’re unaffected (some people truly feel fine with a single drink, others feel quite sedated). And binge drinking is definitely to be avoided – it’s bad for anxiety (causes rebound anxiety) and puts strain on your system alongside the medication.

Key point: Neither mirtazapine nor sertraline mix well with alcohol from a mental health perspective. Alcohol can reduce the effectiveness of the medication and worsen your anxiety/depression overall. If you are taking these meds for anxiety, consider minimizing or abstaining from alcohol for the sake of your progress. If you do drink, do it sparingly and responsibly.

From a medical perspective: On mirtazapine – best to avoid entirely. On sertraline – an occasional small drink may be okay, but check with your doctor and be cautious. And if you notice alcohol makes you feel especially lousy on these meds, that’s a sign to stay away from the booze. Remember, your health comes first – the goal is to reduce anxiety, and alcohol often does the opposite in the long term.

Strengths Available in Australia: Dosage Options and Their Impact

Mirtazapine Strengths: The most common tablet strengths for mirtazapine in Australia are 15 mg, 30 mg, and 45 mg. All these are prescription-only. The usual starting dose is 15 mg per day (at night). Your doctor will often start at 15 mg to see how you tolerate it (especially because of sedation). Many people then increase to 30 mg daily, which is a typical effective dose for anxiety/depression. The effective dose for most people is 30–45 mg per day. In some cases, doses up to 60 mg are used, but 45 mg is more common as an upper end. Notably, mirtazapine’s effects can change with dose: lower doses (15 mg) are more sedating and have more histamine blockade, whereas higher doses (30–45 mg) actually can be less sedating as the noradrenaline effect becomes stronger. This is somewhat counterintuitive – patients often report 15 mg knocks them out, but 30 mg is easier to wake from. Doctors use this knowledge: if someone primarily needs help sleeping and with appetite, 15 mg may be enough; if they need more antidepressant/anxiolytic effect, pushing toward 30 mg or more may yield better mood improvement without as much next-day drowsiness. In Australia, brands like Avanza, Axit, etc., all contain mirtazapine in those strengths (15/30/45). Impact on treatment: Starting at 15 mg helps minimize initial side effects, then going up to 30 mg can provide fuller anti-anxiety effect. If anxiety is not controlled at 30 mg and the person is tolerating it, 45 mg can be tried. Each increment might bring slightly more efficacy but possibly slightly more side effects too (except sedation which sometimes lessens at higher dose as mentioned). Always follow your doctor’s dosing instructions – never adjust the dose without medical advice. And remember, if 15 mg is too sedating, discuss taking it a few hours before bedtime or even splitting dose (though typically it’s given once at night).​

Sertraline Strengths: In Australia, sertraline (Zoloft and generic brands) is commonly supplied in 50 mg and 100 mg tablets. The tablets often have score lines so they can be split (for example, a 50 mg tablet can be halved to 25 mg). There is no 25 mg tablet here as a standalone product, but doctors sometimes start at 25 mg by instructing patients to take half of a 50. The usual starting dose for adults is 50 mg once daily​media.healthdirect.org.au. For certain sensitive individuals or anxiety disorders, a doctor might start at 25 mg for the first week to ease in, then go to 50 mg (as seen in social anxiety disorder recommendations). 50 mg is often the target initial therapeutic dose for anxiety and depression. If needed, the dose can be increased gradually: common next step is 100 mg daily after a few weeks if 50 mg is not sufficient and side effects are tolerable. The maximum dose of sertraline in adults is 200 mg per day – usually achieved by increments (e.g. 50 → 100 → 150 → 200, over weeks). For anxiety disorders, many patients find their optimal dose is in the 100–150 mg range. Panic disorder or OCD often need toward the higher end (150–200 mg), whereas generalized anxiety or social anxiety might do well at 50–100 mg. In Australia, Zoloft® brand comes in 50 and 100 mg, and several generics (e.g. Sertraline Sandoz, APO-Sertraline, etc.) also provide those strengths. Impact on treatment: Lower doses like 25–50 mg may cause fewer side effects initially, but might not fully relieve anxiety if the condition requires a higher serotonin boost. Going up to 100 mg can improve efficacy but you monitor for increased side effects (e.g. at 100 mg, some people might notice more sexual dysfunction or insomnia than at 50 mg). The dose is very individualized – some achieve remission at 50 mg, others need 150 mg. Importantly, titrate slowly according to doctor’s plan, since jumping to high doses won’t make it work faster and could just intensify side effects. Also, there’s no over-the-counter availability of these strengths – you must get them via prescription in Australia (with repeats as needed, often a psychiatrist or GP will provide a script for a few months’ supply if stable, which you can renew via a service like NextClinic or at your GP visits).

In both medications, consistency is key – take them at the same time each day, in the amount prescribed. If you feel your dose isn’t right (too high, too low), talk to your doctor rather than adjusting it yourself. And if you’re on other meds or supplements, always check for interactions that might effectively change how these doses work.

Are They “Sleeping Pills for Flying Anxiety”?

Many people who have fear of flying or flight anxiety wonder if they can take medications like mirtazapine or sertraline to ease their nerves on a plane, perhaps even as a one-time “sleeping pill” for a long flight. This is a nuanced issue, and safety is paramount.

First, it’s important to clarify that mirtazapine and sertraline are not typical acute anti-anxiety pills. They are designed for daily use and have a delayed onset (as discussed earlier, they take weeks to build effect). They are not benzodiazepines (like diazepam/Valium) and will not have an immediate anti-panic effect if you take one dose before boarding. So, if your flight is tomorrow and you’ve never been on these meds, taking a one-off dose of sertraline or mirtazapine is not going to magically calm you – sertraline wouldn’t do anything acute aside from maybe some side effects, and mirtazapine would likely just make you sleepy but not necessarily reduce phobic anxiety in the moment (aside from sedation).

That said, let’s consider two scenarios:

1. Using Mirtazapine as a “sleeping pill” for flying: Mirtazapine at a low dose (7.5–15 mg) is indeed sedating and could knock you out for a few hours. Some doctors might think: if a patient is very anxious about a long flight and wants to sleep through it, could a small dose of mirtazapine be used? In practice, this is uncommon. More frequently, a short-acting sleeping tablet or an anti-anxiety medication (like a benzodiazepine or even melatonin for jetlag) would be used if anything. One reason is that mirtazapine’s sedative effect might be too long-lasting and unpredictable – if you take it, you might be groggy upon landing or for connecting flights. Also, mirtazapine isn’t specifically anti-anxiety in the acute sense; it doesn’t prevent panic, it just sedates. If someone is already on mirtazapine daily for anxiety, they will likely be more at ease flying because their baseline anxiety is treated and they might also sleep easier on the plane due to the drug’s nature. But it’s not prescribed PRN (as-needed) for phobias. Additionally, consider safety: if an emergency happened on the flight, you don’t want to be heavily sedated. This is why many doctors are cautious about prescribing strong sedatives for flights – you need to be able to respond to instructions in the rare event of an emergency​. Deep sedation (whether from benzos or mirtazapine or alcohol) on a flight can also increase the risk of blood clots (DVT) because you’re not moving your legs as much. For these reasons, using mirtazapine explicitly as a “sleeping pill for flying” is generally not recommended by doctors. Non-medical strategies (breathing exercises, meditation, good headphones with calming music, etc.) or therapy for flight anxiety are preferred for occasional fliers.

2. Using Sertraline for flight anxiety: Sertraline again is not an as-needed medication. If you have chronic flying anxiety and you fly frequently, one strategy could be to go on an SSRI (like sertraline) long-term to generally reduce your anxiety, which in turn will make flying easier. In fact, sertraline is indicated for panic disorder and social phobia which share features with flight phobia (situational anxiety). Over months, sertraline could make you less phobic and more willing to fly comfortably. However, taking sertraline on the day of the flight won’t help – in fact, a single dose could cause side effects (nausea or jitteriness) that might make you feel worse on the plane. So, sertraline is only useful for flight anxiety if part of a long-term treatment plan for anxiety; it is not a one-time solution for a flight next week. Many people with a fear of flying will talk to their GP about a benzodiazepine like alprazolam or diazepam for the flight. Indeed, these have been traditionally prescribed – a small dose before boarding can tranquilize the nerves. However, there’s growing reluctance to do this routinely. As one medical source points out, prescribing diazepam (Valium) for flying is no longer recommended due to safety and dependency issues. Benzos can impair your ability to react in an emergency and can, paradoxically, cause some people to become disinhibited or aggressive (rare, but it happens) which on a plane is a big problem. Plus, if you start relying on a benzo for every flight, you might never learn to cope without it, and your anxiety could even reinforce (because you attribute survival to the pill, not your own ability, thus you feel you always need the pill – a psychological crutch).

Given this, what’s the advice? If you really need chemical help for a flight and your doctor agrees, a one-off use of a short-acting sedative might be considered (some doctors might prefer a z-drug like zolpidem to just induce sleep rather than an anti-anxiety per se, or low-dose lorazepam). But neither mirtazapine nor sertraline is ideal for that purpose. Mirtazapine could be considered if you also have insomnia and are starting it for ongoing treatment – you might notice it helps you sleep on the plane as a side benefit. But it’s not a typical prescription just for a flight.

If your question is specifically “Can I take my mirtazapine or sertraline when flying?” – yes, absolutely, continue your prescribed medication on schedule even when you travel. Do not skip doses because you’re flying; maintain your regimen. That will keep your baseline anxiety controlled. Just avoid adding alcohol to self-medicate on top of it (as discussed, alcohol and these meds don’t mix well, especially on a plane where effects can feel stronger due to cabin pressure). If you are hoping for something to take just for the flight, talk to your doctor about alternatives.

Finally, an important note: There’s evidence that repeatedly using sedatives for flight anxiety prevents you from adapting. People don’t get a chance to learn coping mechanisms if they’re always knocked out. Cognitive-behavioral techniques or fear-of-flying courses can be incredibly effective long-term. Medication can be a tool, but try not to rely on the idea of a perfect “sleeping pill for flying anxiety” – it’s better to address the root fear through therapy if possible.

Summary for fliers: Neither sertraline nor mirtazapine is a quick fix on flight day. For short-term flight anxiety relief, they are not suitable “take as needed” options. Mirtazapine will make you sleepy (not necessarily less anxious) and sertraline won’t have an immediate effect at all. If flying triggers major anxiety, consult your GP; they might (with caution) prescribe a small dose of a different anxiolytic just for the flight, or ideally, help you with non-drug strategies. And if you’re already on sertraline or mirtazapine daily, rest assured – being on those medications and generally less anxious overall will likely make the flight more tolerable. Many patients find once their general anxiety is treated, specific fears like flying diminish too.

Comparison Summary: Which Is Better for Your Anxiety?

Mirtazapine vs Sertraline – which one to choose? The answer depends on your specific anxiety profile, health situation, and priorities. Here’s a quick comparison wrap-up:

• Effectiveness for Anxiety: Both medications are effective for anxiety disorders, but sertraline (and SSRIs in general) has a stronger evidence base as a first-line treatment for all major anxiety disorders. Guidelines usually recommend SSRIs (like sertraline) first. Mirtazapine is not typically first-line for anxiety, but it can be very helpful, especially in patients who have anxiety with insomnia, or anxiety with depression that hasn’t responded to SSRIs. Some studies support mirtazapine for generalized anxiety and PTSD, but it’s considered more of a second-line or add-on option. So if you have, say, pure GAD or social anxiety, doctors often try an SSRI (sertraline, escitalopram, etc.) or an SNRI first. Mirtazapine might be considered if SSRIs/SNRIs aren’t suitable or tolerated, or if the person also needs help sleeping and gaining weight.
• Sedation vs Activation: Do you need sedation or not? If you are very anxious and suffering from poor sleep or significant weight loss, mirtazapine’s side effects can be beneficial – it will help you sleep and eat. On the other hand, if daytime drowsiness and potential weight gain are your worst fears, sertraline is the better choice (it’s generally weight-neutral or can even cause mild weight loss initially, and it’s not sedating; some find it mildly energizing which can help daytime functioning). For someone with panic attacks or performance anxiety where sedation would impair function, sertraline (which is non-sedating) would be preferable. Conversely, an anxious person who has trouble sleeping might appreciate mirtazapine’s night-time calm.
• Speed of relief: If rapid relief is desired and the patient is in severe distress, mirtazapine may offer quicker alleviation of anxiety symptoms in the first couple of weeks. Sertraline will work well but requires patience. Some clinicians might start mirtazapine in someone who needs urgent improvement in appetite and sleep, then consider if an SSRI should be added or switched to later for long-term anxiety management.
• Specific Anxiety Conditions: For conditions like Panic Disorder, Social Phobia, OCD, PTSD, sertraline has formal indications and lots of research behind it. Mirtazapine is used off-label for some of these but not as a first-line. For example, in PTSD, mirtazapine can help with insomnia and nightmares, but sertraline is one of the first-line meds for PTSD. In generalized anxiety disorder (GAD), SSRIs/SNRIs are first-line, but mirtazapine has shown benefit in some studies and can be an option, particularly in older patients or those who can’t tolerate SSRIs. If someone has treatment-resistant anxiety/depression, sometimes sertraline and mirtazapine are even used together (this combination is known as “California rocket fuel” when mirtazapine is combined with an SNRI; with SSRIs, it’s less documented but some psychiatrists do combine an SSRI with low-dose mirtazapine for tough cases). That’s only under specialist care though.
• Side Effect Tolerance: Are you more concerned about sexual side effects or about weight gain? Mirtazapine is less likely to cause sexual dysfunction, so for a patient for whom that is a deal-breaker (say a newlywed man who is very concerned about antidepressants affecting his sexual performance), mirtazapine might be preferred. On the flip side, if someone is already overweight or has type 2 diabetes, adding a medication that causes weight gain (mirtazapine) might be undesirable – sertraline might be a better fit as it’s weight-neutral in many people (though note: long-term, SSRIs can cause some weight gain in certain individuals too, but generally less than mirtazapine). For elderly patients, mirtazapine is sometimes chosen to stimulate appetite and sleep, whereas sertraline might cause more agitation or hyponatremia in the elderly. But mirtazapine’s sedative effect in an older person can also raise fall risk, so it’s a balance.
• Comorbidities: If a patient has major depression with anxiety, both can work, but mirtazapine might help more with melancholic features (loss of appetite, severe insomnia) and sertraline might help more with atypical features (like rejection sensitivity, etc.). If a patient has a history of bipolar (where antidepressants can trigger mania), neither is ideal without mood stabilizers, but sertraline has a slightly lower risk of switching someone into mania compared to some other antidepressants. Mirtazapine’s risk in bipolar is not fully clear but any antidepressant can potentially do it. If a patient has significant chronic pain or neuropathy along with anxiety, neither of these specifically addresses pain (an SNRI might be better). If pregnancy is a consideration for a female patient, neither drug is recommended without careful risk assessment (SSRIs carry some small risks in pregnancy; mirtazapine data is limited but it’s sometimes used if needed). These are individual considerations to discuss with a healthcare provider.

In the end, which is “better” comes down to the individual:

• If you need first-line standard anxiety treatment and can tolerate an SSRI, sertraline is often the go-to choice (extensive evidence, broad indications, PBS-covered for those conditions, etc.).
• If you have had issues with SSRIs or your anxiety comes with prominent insomnia or you’ve not responded to first-lines, mirtazapine is a very reasonable option, especially under guidance of a doctor who understands your overall picture.
• Some patients try an SSRI and can’t handle the sexual side effects or the initial jitteriness – for them, mirtazapine can be a savior (it doesn’t cause those, and is generally calming).
• Others might gain a lot of weight on mirtazapine or feel too groggy, and they prefer switching to sertraline for a cleaner feel.

It’s not unusual for a doctor to trial one and then switch if needed. Both can be effective; the goal is to relieve anxiety with manageable side effects. A quick rule of thumb sometimes used: sertraline for the worry in your mind, mirtazapine for the worry in your body (and to rest that body at night). But each also helps the overall psychological state.

Always engage in a shared decision with your healthcare provider about these meds. And remember that medication is one part of anxiety management – therapy (CBT, etc.), exercise, mindfulness, and good lifestyle habits are important companions to pills. In Australia, you can also leverage services like NextClinic for follow-up or prescription management, but you should also have regular check-ins with your GP/psychologist to track progress.

TLDR