Mirtazapine carries one of the lower seizure risks among commonly prescribed antidepressants, though it is not seizure-neutral. In premarketing trials of nearly 2,800 patients, only a single seizure was reported, and the drug’s pharmacological profile suggests it should be relatively safe for the seizure threshold. Yet post-marketing surveillance and newer pharmacovigilance analyses paint a slightly more complicated picture, one worth understanding if you or someone you know takes mirtazapine and has reason to worry about seizures.
How Mirtazapine Works in the Brain
Mirtazapine belongs to a class sometimes called noradrenergic and specific serotonergic antidepressants. It blocks certain receptors on nerve cells in a way that boosts activity of both norepinephrine and serotonin, particularly at one serotonin receptor subtype associated with mood improvement. It also strongly blocks histamine receptors, which is why sedation and weight gain are its most recognizable side effects.1Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy. Mirtazapine: An Antidepressant with Noradrenergic and Specific Serotonergic Effects
What makes this pharmacology relevant to seizures is the norepinephrine piece. Norepinephrine generally acts as a brake on seizure activity in the brain. Animal research has shown that increasing norepinephrine signaling in the hippocampus inhibits limbic seizures, working through a combination of specific receptor subtypes.2PubMed. Pharmacological and neurochemical characterization of the involvement of hippocampal adrenoreceptor subtypes in the modulation of acute limbic seizures Because mirtazapine enhances noradrenergic transmission, there is a theoretical reason to expect it might actually protect against seizures rather than provoke them. That expectation holds up in some lab settings but not perfectly in real-world clinical data.
What Animal Studies Show
Two lines of preclinical evidence are worth knowing about. In a mouse study using standard seizure-induction methods, mirtazapine at a range of doses neither worsened nor improved seizure outcomes compared to controls. The researchers concluded that the drug was essentially seizure-neutral in that acute setting.3PubMed. Mirtazapine does not affect pentylenetetrazole- and maximal electroconvulsive shock-induced seizures in mice
A different study looked at animals that had been kindled to produce chronic seizures, a model meant to mimic epilepsy, and then treated with antidepressants over two weeks. In that experiment, mirtazapine actually showed a mild anticonvulsant effect: seizure severity scores dropped compared to untreated animals, and the time before the first seizure sign increased. The drug did not, however, reduce the total number of severe convulsions.4Journal of Epilepsy Research. Relative Safety of Different Antidepressants for Treatment of Depression in Chronic Epileptic Animals Associated with Depression
So the animal data lean reassuring. But animal seizure models and human seizure risk do not map onto each other perfectly, which is why clinicians pay closer attention to what happens in patients.
Clinical Trial and Surveillance Data
In the original clinical trials that led to mirtazapine’s approval, only one seizure occurred among roughly 2,800 patients, a rate of about 0.04%. Early reviews of the drug described its seizure-inducing potential as “very low.”5PubMed Central. Analysis of the relationship between antidepressants and seizures based on the food and drug administration’s adverse event reporting system database That number was genuinely encouraging, especially compared to older antidepressants like tricyclics that had established reputations for provoking seizures at therapeutic doses.
Post-marketing surveillance, however, has shown that even patients without obvious risk factors for seizures can experience them while on mirtazapine. That same FDA adverse event analysis cautioned that although the risk remains relatively low, clinicians should still exercise care when prescribing it to patients with epilepsy.6PubMed Central. Analysis of the relationship between antidepressants and seizures based on the food and drug administration’s adverse event reporting system database There are also case reports of mirtazapine triggering focal motor seizures and even status epilepticus in individual patients, though these are rare enough to be published as noteworthy clinical observations.7PubMed. Focal motor seizures and status epilepticus provoked by mirtazapine
How Mirtazapine Compares to Other Antidepressants
This is where context matters most. A large analysis of the FDA’s adverse event reporting system ranked antidepressants by their seizure-signal strength. Bupropion was the clear outlier at the top, with a reporting odds ratio around 8.6, meaning seizure reports were roughly eight and a half times more common with bupropion than the background rate for all drugs in the database. Mirtazapine came in with a ratio of about 3.0, sitting in the middle of the pack alongside venlafaxine and several tricyclics. Sertraline and paroxetine had lower ratios, around 2.0 and 1.3 respectively.8PubMed Central. Analysis of the relationship between antidepressants and seizures based on the food and drug administration’s adverse event reporting system database
A few things are important to understand about these numbers. Adverse event reporting databases capture spontaneous reports from clinicians and patients, so they do not prove that a drug caused a seizure. People who take mirtazapine might have other risk factors for seizures. The ratio is a signal of disproportionate reporting, not a direct measure of seizure incidence. Still, the ranking is broadly consistent with what clinicians observe: mirtazapine is safer than bupropion and the older tricyclics, roughly comparable to venlafaxine, and possibly slightly riskier than some SSRIs like sertraline or paroxetine.
A separate nationwide case-control study looking at new epilepsy diagnoses in antidepressant users found mirtazapine associated with a modestly elevated risk, with an odds ratio of about 1.56 compared to non-users. Several other antidepressants, including escitalopram and venlafaxine, showed similar or higher associations in the same analysis.9PubMed. Antidepressant drugs use and epilepsy risk: A nationwide nested case-control study Whether this reflects the drugs themselves or the underlying depression driving prescriptions (depression independently raises seizure risk) remains an open question that no study has fully untangled.
Cortical Excitability, Not Just Seizure Counts
One finding that adds some nuance involves a study measuring cortical excitability directly. Researchers used transcranial magnetic stimulation to test how mirtazapine changed the brain’s threshold for electrical excitation in both healthy volunteers and epilepsy patients with depression. They found that mirtazapine lowered the activation threshold in both groups, meaning the brain’s motor cortex became easier to excite after a dose.10Journal of Neurology, Neurosurgery & Psychiatry. Mirtazapine increases cortical excitability in healthy controls and epilepsy patients with major depression
Increased cortical excitability does not automatically mean you will have a seizure. The brain has multiple layers of inhibitory safeguards, and the step from “slightly easier to excite in a lab measurement” to “actual clinical seizure” is a large one. But the finding does suggest that calling mirtazapine purely seizure-protective oversimplifies things. It may raise excitability at the cortical level while the noradrenergic boost provides some counterbalancing protection against seizure spread. The net effect for most people is still safe, but the margin may be thinner than the animal data alone would suggest.
Mirtazapine in People Who Already Have Epilepsy
Depression is extremely common in people with epilepsy, affecting roughly a third or more of that population. Yet many patients go untreated because of fears, sometimes shared by their doctors, that antidepressants will make seizures worse. Expert reviews have argued for years that this concern is overblown and that leaving depression untreated usually poses a greater risk than prescribing an appropriate antidepressant. Mirtazapine, alongside citalopram and sertraline, is considered among the safer first-line options for depressed epilepsy patients.11PubMed. Treatment of depression in patients with epilepsy
Bupropion, by contrast, is the one antidepressant that epilepsy treatment guidelines consistently recommend avoiding, given its significantly higher seizure signal. The guidance on mirtazapine is more permissive: it is generally considered acceptable, though clinicians may want to monitor seizure frequency when starting it, particularly in patients whose seizures are not well controlled.
What Happens in Overdose
Overdose data provide another lens for evaluating seizure risk. A study of mirtazapine overdoses found that no patient who ingested mirtazapine alone had a seizure, even at doses well above the therapeutic range. Sedation was the dominant effect, and the researchers concluded that mirtazapine overdose is unlikely to cause major toxicity.12PubMed Central. Mirtazapine overdose is unlikely to cause major toxicity This is a meaningful safety margin. Many drugs that lower the seizure threshold at therapeutic doses become genuinely dangerous in overdose. Mirtazapine’s clean overdose profile adds weight to the idea that its seizure risk at normal doses is low.
Interactions with Anti-Seizure Medications
If you take mirtazapine alongside anti-seizure drugs, the interactions go mostly in one direction: the seizure medication may reduce mirtazapine’s effectiveness, not the other way around. Carbamazepine, a widely used anti-seizure drug, is a potent inducer of the liver enzymes that break down mirtazapine. In a study of healthy volunteers, adding carbamazepine roughly halved mirtazapine’s blood levels, which means the antidepressant dose may need to be increased to remain effective.13PubMed. Drug-drug interaction studies with mirtazapine and carbamazepine in healthy male subjects Reassuringly, mirtazapine did not alter carbamazepine levels or interfere with its enzyme-inducing properties, so seizure control should not be compromised by adding the antidepressant.
Phenytoin, another anti-seizure medication, showed a similar pattern. Phenytoin roughly halved mirtazapine blood levels through the same enzyme-induction mechanism, while mirtazapine had no effect on phenytoin’s levels.14PubMed. Concomitant use of mirtazapine and phenytoin: a drug-drug interaction study in healthy male subjects The practical takeaway is straightforward: if you are on carbamazepine or phenytoin and start mirtazapine, your doctor may need to prescribe a higher mirtazapine dose. Your seizure medication levels should remain stable.
Sex Differences in Reporting
A recent pharmacovigilance analysis examining sex-specific drug safety signals found that mirtazapine appeared among the drugs with notable seizure and myoclonus signals specifically in female reports. The signal was not prominent among male reports for the same drug.15PubMed Central. Sex-specific pharmacovigilance signals and time-to-onset patterns of drug-related myoclonus and epileptic seizures: a real-world pharmacovigilance analysis This does not necessarily mean women face a higher biological seizure risk from mirtazapine. Women and men are prescribed different drugs at different rates, metabolize medications differently due to body composition and hormonal factors, and report adverse events at different rates. But the finding is a reminder that seizure risk from any medication can be influenced by factors beyond the drug itself, and it suggests that sex-specific monitoring may deserve more attention in future research.
Stopping Mirtazapine and Seizure Risk
Most discussions about antidepressants and seizures focus on what happens while you are taking the drug. But discontinuation deserves mention too. A systematic review of antidepressant withdrawal phenomena documented that stopping mirtazapine can produce a discontinuation syndrome, and case reports have described severe withdrawal reactions including movement abnormalities and paradoxical activation.16Deutsches Ärzteblatt International. Antidepressant Withdrawal and Rebound Phenomena: A Systematic Review While seizures specifically during mirtazapine withdrawal are not well documented in the literature, the principle that abrupt discontinuation of drugs affecting brain chemistry can temporarily destabilize neural excitability is well established. Tapering off gradually rather than stopping suddenly is standard practice for mirtazapine, as it is for most antidepressants.
When the Noradrenergic Theory Breaks Down
The idea that mirtazapine’s norepinephrine-boosting action should protect against seizures is tidy, but the brain does not operate as a single dial. The cortical excitability data mentioned earlier suggest that the drug’s effects on neuronal firing thresholds are more complex than “more norepinephrine equals fewer seizures.” The serotonergic effects add another layer: mirtazapine blocks certain serotonin receptor subtypes while allowing increased activity at others, and different serotonin pathways can either promote or inhibit seizure activity depending on which receptors and brain regions are involved.
The histamine blockade may actually be doing some quiet protective work. Histamine H1 receptor antagonism has sedating effects, and sedation broadly tends to raise the seizure threshold by dampening overall neural excitability. This might help explain why mirtazapine’s seizure profile is better than you might expect from its excitability data alone, and why overdoses that produce deep sedation do not produce seizures. But this is speculative territory. No one has run the controlled trial that would isolate each receptor’s contribution to seizure risk in humans.
The honest summary is that mirtazapine’s net effect on seizure threshold in a given person depends on the balance of multiple pharmacological actions, and individual variation in brain chemistry, genetics, and concurrent medications all shift that balance. For the vast majority of patients, the balance tips toward safety. For a small number, it does not, and we cannot yet predict reliably who those people will be.
Practical Considerations if You Are Concerned
If you have no history of seizures and are being prescribed mirtazapine for depression, anxiety, or insomnia, the seizure risk is very low and should not by itself be a reason to avoid the drug. The 0.04% rate from clinical trials, the clean overdose data, and its favorable comparison to many alternatives all support this.
If you have epilepsy or a history of seizures, mirtazapine remains a reasonable antidepressant option, and expert reviews list it alongside sertraline and citalopram as a first-line choice. The key is communication with whoever manages your seizure care. If you are on carbamazepine or phenytoin, your mirtazapine dose will likely need to be higher than standard because those medications accelerate how your body clears the antidepressant. And if your seizure control changes after starting or stopping mirtazapine, that information matters for your neurologist even if the connection is not certain.
What you should not do is avoid antidepressant treatment altogether out of seizure fear. Untreated depression worsens seizure control in people with epilepsy, and the risk of leaving it untreated usually outweighs the small added seizure risk from drugs like mirtazapine.17PubMed. Treatment of depression in patients with epilepsy The one antidepressant that most guidelines agree should genuinely be avoided in seizure-prone individuals is bupropion, which carries a meaningfully higher signal than anything else on the list.