Here is a number that should change how you think about your first year of prescribing: roughly 40% of patients who start an oral antipsychotic are off it within three months. Not a year. Three months.
That figure comes from a large pharmacy-records study that The Carlat Psychiatry Report reviewed in its October 2026 issue, and the headline finding is the part that will stick with you. Of all the oral antipsychotics compared, the one patients stayed on longest was clozapine, the drug most clinicians treat as a last resort, and the one many new prescribers are quietly afraid of.
If you are studying for boards right now, I want you to read this one slowly. Not because it is a trick question waiting to happen (though clozapine absolutely shows up on exams), but because it points at a gap between what the evidence says and what actually happens in clinic. Closing that gap is going to be part of your job.
What the study actually found
The Carlat review, written by Dr. Jesse Koskey, covers a paper by Parabiaghi and colleagues in Pharmacopsychiatry (2025;58(4):159–169). It is a population-based cohort study built on pharmacy dispensing records. It followed more than 42,000 adults who started an oral antipsychotic between 2001 and 2021. The main follow-up window was three months, with secondary analyses stretching out as far as twenty years.
A few details worth writing on a flashcard:
Second-generation antipsychotics held on to patients better than first-generation agents, with a hazard ratio of 0.76 (95% CI 0.73 to 0.79). Remember how to read that: a hazard ratio below 1 means a lower hazard of stopping, so patients on second-generation drugs were less likely to quit, not more.
Clozapine’s median persistence was 175 days. Other agents landed between 92 and 133 days. Against olanzapine the hazard ratio was 0.85 (95% CI 0.79 to 0.91), and against risperidone it was 0.80 (95% CI 0.74 to 0.87). Quetiapine had the poorest persistence of the group, even though it was the second most prescribed.
And the sobering one: by the one-year mark, about 80% of patients had discontinued their initial agent, and only 1% of them were later re-prescribed that same drug. When a patient walks away from an antipsychotic, they usually do not come back to it.
Why clozapine sticking is surprising
Think about everything clozapine asks of a patient. Blood draws. Slow titration. Sedation, drooling, constipation. A reputation that precedes it. If any drug should have terrible persistence, you would bet on this one.
Yet it outlasted the easier options. That is a clue worth sitting with. Patients tend to stay on a medication when they feel it working, and clozapine is the drug we reach for in the people who have failed everything else. For someone who has cycled through several agents without relief, finally feeling better is a powerful reason to put up with the inconvenience.
Dr. Koskey’s takeaway in the Carlat review is blunt: clozapine is underused, and the line he lands on is that clinicians should be using it more often than they do. The review also notes that clozapine had one of the lowest prescription counts among the U.S.-available agents in the data.
Be honest about what this study can’t tell you
Here is where I want you to build a habit that will serve you on exams and with patients. A pharmacy-records study is a record of what was dispensed. It does not contain diagnoses. It does not contain clinical outcomes. And it cannot confirm that anyone actually swallowed the pills.
Carlat’s reviewer flags exactly these limits. There is also a selection issue hiding in plain sight: people who start clozapine are, by definition, a different group from people who start a first antipsychotic for a first episode. Persistence may partly reflect who gets the drug, not only what the drug does. Staying on a medication is not the same as being well on it.
So treat this study as a strong signal, not a verdict. It fits a larger picture, and that is where the evidence gets more convincing.
The wider picture: why people stop clozapine
A 2026 systematic review and meta-analysis in Schizophrenia Bulletin Open pooled 45 observational studies and estimated that about 34% of people prescribed clozapine discontinue it (95% CI 29% to 40%). Among the whole treated population, roughly 11% stopped because of non-adherence, 11% because of side effects, and 7% because it was not working. Among those who did stop, non-adherence accounted for about 35% of discontinuations and side effects for about 34%.
The authors also caution that heterogeneity across the studies was very high and that reasons for stopping are inconsistently reported, so those numbers are best read as a range rather than gospel. Still, look at what they say. Lack of efficacy is the smallest slice. Most of the people who leave clozapine are leaving because of things a good prescriber can often work on: side effects that can be managed, and adherence barriers that can be talked through.
That is a hopeful message for those of us who will be doing the managing.
What the guidelines say you should be doing
The American Psychiatric Association’s practice guideline for schizophrenia (third edition, 2020) recommends clozapine for patients with treatment-resistant schizophrenia. It also recommends clozapine when suicide risk stays substantial despite other treatment, and for persistent aggressive behavior. Those three indications are board-exam material, so memorize them.
Treatment resistance itself has a definition, and it is stricter than most students assume. The Treatment Response and Resistance in Psychosis (TRRIP) working group consensus, published in the American Journal of Psychiatry in 2017, calls for at least two adequate antipsychotic trials, each lasting a minimum of six weeks at a dose equivalent to at least 600 mg of chlorpromazine daily, with adherence confirmed. That last piece matters. A patient who “failed” two drugs but never really took them has not yet shown treatment resistance.
This is a place where your training will make you better than the average prescriber. Before you label someone treatment resistant, check dose, duration, and adherence. Before you give up on a drug you have sent to a patient who stopped it, ask what happened.
Remove the barrier you were taught to fear
One reason clozapine feels intimidating is that the monitoring requirements used to be a federal program. The FDA ended the clozapine REMS, and we covered what that change means for practice in an earlier post here. The need for sensible absolute neutrophil count monitoring has not disappeared, and you should still know the schedule your setting follows. But the sense that a government registry stands between you and the prescription is gone.
If you have been avoiding clozapine because the paperwork felt like a wall, that wall is a lot lower than it was.
How this shows up on your exam
Expect clozapine to appear in a few forms. A vignette describing a patient who has failed two antipsychotic trials, asking for the next best step. A question about the indication for persistent suicidality in schizophrenia. A question on the adverse effects you must monitor: severe neutropenia, myocarditis in the early weeks, seizure risk, metabolic effects, and constipation that can progress to something dangerous. Another classic: how smoking changes clozapine levels, which we have written about before.
The twist this study adds is conceptual rather than factual. Newer exam items increasingly ask you to reason about adherence and shared decision making, not just recite the drug list. If a stem tells you a patient stopped their medication, the strongest answer is often the one that explores why before switching agents.
What I’d want you to carry into clinic
First, expect people to stop. If 40% of starts are over in three months, then the first follow-up visit is not a courtesy; it is where the treatment succeeds or fails. Schedule it early. Ask directly about side effects before the patient decides they are not worth it.
Second, do not let reputation make your decisions. Clozapine’s fearsome name has quietly kept it away from people who are likely to benefit. Knowing the real risks, and the real monitoring plan, lets you offer it with confidence rather than avoiding it out of habit.
Third, read research the way Dr. Carlat has long taught clinicians to read it. Ask what was measured, who was in the sample, and what the study cannot say. This one measured dispensing. It did not measure recovery. Hold both of those thoughts at once.
Finally, remember who is on the other side of these numbers. Behind a persistence curve is a person deciding, again and again, whether the medication is worth it. Your job is to make that decision easier to say yes to.
You are closer than you think
I know the pharmacology can feel endless. Every drug has its monitoring rules, its interactions, its exceptions, and clozapine has more than most. But notice what just happened: you read a pharmacy-database study, understood its limits, connected it to a guideline, and pulled out exam-ready facts. That is exactly the thinking boards reward and patients deserve.
Keep going. Build the habit of asking not only what the drug does, but whether the patient can stay on it. That question will make you a better prescriber than most people who walk into their first job.
Ready to turn this kind of clinical reasoning into exam-day confidence? Head to PMHNPReview.org for practice questions and study tools built for future psychiatric nurse practitioners.
Sources discussed: The Carlat Psychiatry Report (October 2026, review by Jesse Koskey, MD, of Parabiaghi et al., Pharmacopsychiatry 2025); Schizophrenia Bulletin Open (2026) systematic review and meta-analysis of clozapine discontinuation; American Psychiatric Association Practice Guideline for the Treatment of Patients With Schizophrenia, 3rd ed. (2020); Howes et al., TRRIP consensus, American Journal of Psychiatry (2017). This post is educational and is not medical advice.