Prescribing Xanomeline-Trospium

Why Xanomeline-Trospium Matters

Xanomeline-trospium (Cobenfy) is the first drug approved for schizophrenia that works through the muscarinic (acetylcholine) system, a departure from the dopamine receptor mechanisms that have run the field since chlorpromazine. Xanomeline is a muscarinic agonist with its strongest activity at M1 and M4 receptors in the brain. Trospium is an old overactive-bladder drug that blocks muscarinic receptors mainly in peripheral tissues, and it is in the capsule to keep xanomeline's gut and gland effects tolerable. The FDA approved the pair for schizophrenia in adults in September 2024, and that is still its only indication.

Efficacy in acute schizophrenia looks like that of the established drugs. Effect-size estimates run from 0.56 to 0.65 (the higher figure from the sponsor's pooled analysis of three 5-week trials), in the same range as other antipsychotics. The side-effect list is different. Akathisia, parkinsonism, sedation and weight gain ran near placebo in the short trials, prolactin did not rise, and the label carries no boxed warning and none of the usual antipsychotic class warnings. In their place you get nausea, dyspepsia, constipation, vomiting, a faster heart rate, some blood pressure elevation, and a set of anticholinergic risks (urinary retention, narrow-angle glaucoma, slowed gut motility) that most psychiatrists have not had to screen for with an antipsychotic.

It also asks more of the patient than most antipsychotics do. It is taken twice daily on an empty stomach, titrated over a week, kept away from patients with moderate or severe kidney impairment or any liver impairment, and it is brand-only at a launch price of about $1,850 a month.

Part 1: Indications

FDA-Approved Uses

• Schizophrenia (adults)

Not approved: adjunctive use with another antipsychotic, bipolar disorder, psychosis in Alzheimer's disease or other dementias, and patients under 18. The label revision checked for this guide (DailyMed, revised January 2026) lists schizophrenia in adults and nothing else.

Off-Label / Emerging

• Adjunctive treatment in schizophrenia: one negative phase 3 trial (ARISE, below), so keep it to monotherapy until there is more data.
• Psychosis in Alzheimer's disease: the phase 3 ADEPT program is still running, and no results have been reported. Until they are, there is no evidence for this use, and the label's data in older adults are thin (Part 9).
• Bipolar I mania: two phase 3 trials (BALSAM-1 and BALSAM-2) are recruiting on ClinicalTrials.gov. There is no published efficacy data.
• Cognition in schizophrenia: the trials found no improvement on cognitive testing overall. A secondary analysis restricted to patients with marked cognitive impairment did find one (Horan et al., Am J Psychiatry 2025). Treat that as a hypothesis.

The Evidence by Indication

Acute schizophrenia. Three 5-week, placebo-controlled, inpatient trials in adults with an acute exacerbation were all positive. EMERGENT-1 was the phase 2 trial (Brannan et al., N Engl J Med 2021), with a placebo-subtracted PANSS improvement of 11.6 points (Cohen's d 0.81). The two phase 3 trials are the ones in the label. In EMERGENT-2 (Kaul et al., Lancet 2024; 252 patients at 22 US sites), PANSS total fell 21.2 points vs 11.6 on placebo, a difference of 9.6 (95% CI 13.9 to 5.2), effect size 0.61. In EMERGENT-3 (Kaul et al., JAMA Psychiatry 2024), it fell 20.6 vs 12.2, a difference of 8.4 (CI 12.4 to 4.3), effect size 0.60. The pooled analysis of all three (Kaul et al., Schizophrenia 2024; 640 patients) gave a 9.9-point difference (d 0.65), with 41.4% vs 20.9% reaching at least 30% PANSS improvement. Separation from placebo appeared within two weeks.

Trial patients were hospitalized, mostly Black (68%) and male (75%), median age 46, with nobody over 65. The trials excluded treatment resistance (failure of two adequate trials) and comorbid substance use disorders, and allowed no other psychotropics apart from as-needed benzodiazepines and hypnotics.

Negative symptoms. In the pooled analysis, the PANSS negative subscale improved more than on placebo (1.7 points, d 0.40), smaller than the positive-subscale effect (3.2 points, d 0.67). Negative symptoms tend to improve whenever positive symptoms are treated, so this is not evidence that it treats the chronic primary negative symptoms that drive disability.

Adjunctive use (ARISE). In this 6-week outpatient trial, adults with an inadequate response to their current atypical antipsychotic had xanomeline-trospium or placebo added. The difference on PANSS total was 2.0 points at week 6 and missed significance (P = .11), per the sponsor's April 2025 announcement. A post hoc split found no benefit when the background drug was risperidone (P = .66) and a significant difference with the other antipsychotics (P = .03). Post hoc subgroups in a failed trial are a reason to run another trial and do not support routine add-on use.

Long-term data. Two 52-week open-label studies (EMERGENT-4, an extension with 156 patients, and EMERGENT-5, with 566) found no new safety signals. In EMERGENT-4, 69% had at least a 30% PANSS improvement and mean weight changed by -1.9 kg from the acute-trial baseline, but only 34 of the 156 enrolled (22%) completed the year (Kaul et al., Am J Psychiatry 2026), so those figures describe the patients who stayed. About half left EMERGENT-5 early, and there only 30% reached a 30% improvement. Across the pooled 718 long-term patients, 18% stopped because of adverse effects, mainly gastrointestinal. There are no randomized relapse-prevention data yet. A randomized withdrawal maintenance trial (NCT07686263, about 472 patients) began in August 2026, with completion estimated for 2029.

Alzheimer's disease psychosis (ADEPT). BMS reported irregularities at a small number of ADEPT-2 sites in late 2025, excluded those sites and enrolled more patients. On its July 2026 earnings call it said ADEPT results would start arriving in early 2027 and be spread across that year, citing slow enrollment in ADEPT-2 and ADEPT-4 and slow accrual of relapse events in ADEPT-1.

Who Is a Good Candidate?

• An adult with schizophrenia who stopped D2 drugs because of akathisia, parkinsonism, prolactin effects or sedation
• A patient for whom weight gain or metabolic risk rules out olanzapine, clozapine or quetiapine
• A patient who can reliably take a capsule twice a day away from meals
• eGFR 60 or higher and no known liver impairment

Who Is a Poor Candidate?

• Urinary retention, gastric retention, moderate or severe hepatic impairment, or untreated narrow-angle glaucoma (all contraindications)
• Mild hepatic impairment, eGFR below 60 mL/min, or active biliary disease such as symptomatic gallstones (not recommended in the label)
• An older man with symptomatic prostate enlargement, or anyone with incomplete bladder emptying
• Treatment-resistant schizophrenia; it has not been studied there, and clozapine is the evidence-based step
• A patient who cannot manage twice-daily dosing on an empty stomach, or one for whom a long-acting injectable is the adherence plan (there is no injectable form)
• A patient on a heavy anticholinergic load that cannot be reduced

Part 2: Mechanism

The label calls xanomeline's mechanism in schizophrenia unclear and attributes its efficacy to agonist activity at M1 and M4 muscarinic receptors in the central nervous system. These receptors sit in cortical and striatal circuits involved in psychosis, and activating them may rebalance dopamine and glutamate signaling indirectly.

• Xanomeline: binds all five muscarinic subtypes with similar affinity (Ki 10, 12, 17, 7 and 22 nM for M1 through M5) but has higher agonist activity at M1 and M4. It has no direct action at dopamine receptors, which fits the near-placebo motor effects and the lack of prolactin elevation.
• Trospium: a quaternary ammonium muscarinic antagonist that acts mainly in peripheral tissues. It crosses the blood-brain barrier poorly, which lets xanomeline act centrally while trospium blunts sweating, salivation and diarrhea in the body. The label still lists trospium-related central effects (dizziness, confusion, hallucinations, somnolence), so central anticholinergic effects still occur, especially in older patients.

The combination exists because xanomeline alone failed on tolerability. In the 1990s Alzheimer's trials it improved cognition and behavior, but more than half the patients dropped out with nausea, diarrhea and sweating (Bodick et al., Arch Neurol 1997). The trade-off the capsule makes is to swap those cholinergic effects for trospium's anticholinergic ones: dry mouth, constipation, urinary retention and a faster heart rate.

Pharmacokinetics. Both components have short half-lives (about 5 hours for xanomeline and 6 hours for trospium), so dosing is twice daily. Peak levels come at about 2 hours (xanomeline) and 1 hour (trospium), and steady state takes 3 to 5 days. Xanomeline exposure rises more than proportionally with dose: going from 100 mg/20 mg to 125 mg/30 mg twice daily raised xanomeline AUC and Cmax by about 50%. Xanomeline is metabolized by CYP2D6, 2B6, 1A2, 2C9 and 2C19 and by flavin monooxygenases, with CYP2D6 a significant contributor. Trospium is mostly excreted unchanged in urine (85% to 90%) by active tubular secretion, so kidney function governs its levels.

Part 3: Before You Start: Workup and Candidacy

The label asks for two things before the first dose: liver enzymes with bilirubin, and heart rate. Everything else below comes from the contraindications and warnings, which turn the history into the main screening tool.

The consensus panel convened in 2025 (J Clin Psychiatry 2025, "Real-World Implementation of Xanomeline-Trospium in Schizophrenia") also recommends a review aimed at cutting unnecessary anticholinergic burden before starting, with particular attention to medicines for sleep, bladder control, COPD, Alzheimer's disease and Parkinson's disease. A patient coming off a D2 antagonist may still be on benztropine or another anticholinergic for side effects of the old drug; decide whether it is still needed.

Part 4: How to Start and Dose

The Titration

The label schedule is fixed: 50 mg/20 mg twice daily for at least two days, then 100 mg/20 mg twice daily for at least five days, then an optional step to 125 mg/30 mg twice daily. In the trials, patients moved to 125 mg/30 mg on day 8 unless they could not tolerate it, and anyone could drop back to 100 mg/20 mg for the rest of the study. At least 90% of trial patients reached and tolerated the top dose. That last step raises xanomeline exposure by about 50%, and the label notes that urinary retention was seen mainly at the maximum dose.

Outpatients often need a gentler pace than inpatients. The 2025 consensus panel suggests starting outpatients at 50 mg/20 mg twice daily for 1 to 2 weeks, then titrating by response and tolerability, and says many patients settle between 100 mg/20 mg and 125 mg/30 mg twice daily. That stays within the label, which sets only minimum durations for each step. From here to the end of Part 4, the outpatient pace, dose timing, switching and restarting advice is consensus or practice; the label is silent on all four.

Timing and Food

Both doses go at least 1 hour before a meal or at least 2 hours after one, and the capsules are swallowed whole. Twice-daily dosing away from food is the hardest part for many patients, so build it into the day. On waking (an hour before breakfast) and at bedtime (two hours after dinner) works for most people. Ask about meal timing at every early visit, because dosing with food lowers trospium sharply (Part 2).

Getting Through the First Two Weeks

In the pooled 5-week trials, cholinergic adverse events peaked around day 7 (28.8% of patients that day), generally began within the first two weeks, and lasted on average from 4 days (vomiting) to 20 days (dry mouth) (Kaul et al., J Clin Psychiatry 2025). Tell patients that before the first dose. The consensus panel recommends prescribing ondansetron 4 mg for the first 14 days, with a repeat dose after 30 minutes if nausea persists, to reduce early dropouts. Ondansetron has its own costs here: it constipates, which stacks on trospium's 17% constipation rate, and its label carries QT and serotonin syndrome warnings, so check bowels and look at QT-prolonging and serotonergic co-medications before you add it. Staying at 100 mg/20 mg instead of moving to the top dose is the other lever, as the trials allowed.

Switching From Another Antipsychotic

The label has no switching instructions. In the pivotal trials, patients started xanomeline-trospium without other antipsychotics on board. One open-label switching trial has since reported (NCT06924255; 105 stable outpatients; presented in 2026): a 2-week and a 4-week taper of the prior atypical gave similar safety and symptom scores, discontinuation was 15% with the 2-week taper and 26% with the 4-week taper (not significant), and 86% reached 125 mg/30 mg. It had no placebo or active comparator. A cross-taper over about two weeks, which also avoids withdrawal symptoms from the old drug, is a reasonable default. During the overlap, a highly anticholinergic antipsychotic such as clozapine or olanzapine adds to trospium's anticholinergic effects, so watch bowels and bladder closely in that window (the label's antimuscarinic interaction, applied to the switch).

Restarting After a Gap

The label does not say how to restart after missed days. Because tolerability depends on the stepwise start and both components clear within about a day, re-titrating from 50 mg/20 mg after several days off is a cautious choice.

Dose Adjustments and Special Populations

• Hepatic: xanomeline Cmax and AUC were 2.8 and 2.6 times normal in mild (Child-Pugh A) impairment and at least 7 times normal in moderate (B) impairment. Mild impairment is not recommended; moderate and severe are contraindicated.
• Renal: trospium AUC was 1.6 times normal in mild, 2.2 times in moderate and 2.9 times in severe impairment, with xanomeline also rising (1.9 to 2.4 times). The label keeps the usual dose in mild impairment and does not recommend use below eGFR 60.
• Geriatric: trospium AUC was 60% higher at 65 and older. Maximum 100 mg/20 mg twice daily.
• CYP2D6: intermediate metabolizers had 28% higher xanomeline Cmax and ultrarapid metabolizers 43% lower exposure; poor metabolizers have not been characterized. There is no genotype-based dose instruction.
• Body weight: exposure was 20% to 35% lower at 120 kg than at 70 kg, which the label judges not clinically meaningful.

Part 5: Monitoring

The label requires liver tests and heart rate at baseline and then "as clinically indicated," without a fixed schedule. The follow-up intervals below are practice, built on the timing of events in the trials.

Part 6: Side Effects and How to Manage Them

Rates below are drug vs placebo from the label's pooled 5-week trials (251 vs 253 patients) unless stated. Discontinuation for adverse reactions was 6% vs 4%, led by nausea (2%) and vomiting (1%). The label's most common adverse reactions, at 5% or more and at least twice placebo, were nausea, dyspepsia, constipation, vomiting, hypertension, abdominal pain, diarrhea, tachycardia, dizziness and gastroesophageal reflux.

Nausea, Vomiting, Dyspepsia and Reflux

Nausea was 19% vs 4%, dyspepsia 18% vs 5%, vomiting 15% vs 1%, abdominal pain 8% vs 4%, diarrhea 6% vs 2% and reflux 5% vs under 1%. These are the xanomeline effects that trospium only partly covers, and they cluster in the first two weeks.

• Management: confirm the empty-stomach timing, consider ondansetron for the first two weeks (consensus panel), and hold at 100 mg/20 mg if the top dose brings them back. New dyspepsia, nausea, vomiting or upper abdominal pain later in treatment needs a look for gallbladder, biliary or pancreatic disease, as the label directs.

Constipation and Dry Mouth

Constipation was 17% vs 7% and dry mouth 4% vs 2%. Trospium slows gut motility, and gastric retention is a contraindication. GLP-1 agonists also slow the gut, so the combination may cause trouble.

• Management: ask about bowel habit at each early visit, treat constipation early, and trim other anticholinergics. Remember that ondansetron, if you added it for nausea, also constipates. Be more careful in a patient also taking clozapine.

Heart Rate and Blood Pressure

Tachycardia was reported in 5% vs 2%. Mean heart rate rose most on day 8 (13.5 bpm vs 4.0 on placebo) and eased to 11.4 vs 5.5 bpm by week 5. In a dedicated 8-week ambulatory study, 24-hour heart rate was up 9.8 bpm. Hypertension, a grouped term that includes blood pressure increases, was 11% vs 2%. Mean changes were small by week 5 in the pooled trials (systolic +0.7 vs 0.0 mm Hg, diastolic +1.9 vs 0.4), with the peak in the first week (Kaul et al., 2025). Postmarketing reports with trospium include supraventricular tachycardia, palpitations, syncope and hypertensive crisis.

• Management: check pulse and blood pressure at early visits. In a patient with coronary disease, arrhythmia or poorly controlled hypertension, decide whether a sustained rise of about 10 bpm is acceptable before you start.

Urinary Retention

Retention was uncommon in the 5-week trials (0.8% vs 0.4%) but reached 3.5% in the long-term open-label studies, where urinary tract infections were reported in 2.3%. It was more common in men, older patients and those with risk factors, occurred at all doses, and was seen mainly at the maximum dose. Across 1,594 people exposed, four needed a Foley catheter.

• Management: the label offers dose reduction, stopping the drug, or urology referral. A patient who cannot urinate needs urgent care.

Liver Enzymes and the Biliary Tree

ALT or AST rose to 3 times the upper limit of normal or more in 2.8% vs 0.4%. Most elevations came in the first month and resolved on continued treatment; some needed an interruption, and one came with a bilirubin rise. The label describes a pattern of short-lived enzyme spikes with rapid decline, consistent with transient biliary obstruction from gallbladder contraction and possible stone passage. Stop the drug for jaundice, pruritus, or ALT above 5 times the upper limit of normal or 5 times baseline.

Dizziness, Somnolence and Anticholinergic CNS Effects

Dizziness was 5% vs 2% and somnolence 3% vs 2%. Blurred vision (3% vs 0%) and orthostatic hypotension (2% vs 1%) were also reported. The label warns that trospium can cause confusion, hallucinations and somnolence, with confusion and delirium among the postmarketing reports. If a patient's psychosis seems to worsen soon after a dose increase, consider anticholinergic toxicity before you call it a failed drug; the label advises dose reduction or stopping when these effects appear.

Extrapyramidal Symptoms and Akathisia

Non-akathisia EPS events were 2% vs under 1% in the label. In the pooled safety analysis, akathisia was reported in 2.4% vs 0.9%, most EPS events were judged unrelated to treatment (1.5% vs 0.3% treatment related), there were no reports of tardive dyskinesia, and Simpson-Angus, Barnes and AIMS changes were close to zero. The authors note that 4 of the 8 akathisia cases came from a single EMERGENT-3 site and may have been agitation from psychosis. Salivary hypersecretion was 2% vs 0%.

Metabolic (Weight, Glucose, Lipids)

Over 5 weeks, weight rose 1.41 kg vs 1.94 kg on placebo, and 5.3% vs 11.4% gained 7% or more of body weight. Mean weight fell over a year in the open-label studies (-1.9 kg in EMERGENT-4). In a 2025 meta-analysis, triglycerides rose more often than on placebo; weight, glucose and cholesterol did not change. Check lipids as you would for any antipsychotic.

Angioedema

Angioedema of the face, lips, tongue or larynx has been reported with the combination and with trospium alone, once after the first trospium dose. Stop the drug if the tongue, hypopharynx or larynx is involved, and secure the airway. A history of hypersensitivity to trospium is a contraindication. Postmarketing reports with trospium also include anaphylaxis, Stevens-Johnson syndrome and rhabdomyolysis, so a new rash, hives or severe muscle pain needs a look.

Part 7: Toxicity, Overdose, and Boxed Warnings

Contraindications

• Urinary retention
• Moderate (Child-Pugh B) or severe (Child-Pugh C) hepatic impairment
• Gastric retention
• History of hypersensitivity to xanomeline-trospium or trospium chloride (angioedema has been reported)
• Untreated narrow-angle glaucoma

Other Serious Risks

The label's other warnings are urinary retention, mild hepatic impairment, active biliary disease, decreased GI motility, narrow-angle glaucoma, heart rate increase, renal impairment below eGFR 60 and anticholinergic CNS effects. Parts 3 and 6 cover how to screen for and manage each. Two points are not made elsewhere: with known narrow angles, use it only if the benefit outweighs the risk and with careful monitoring, and tell patients not to drive or run machinery until they know how it affects them.

Overdose

Part 8: Drug Interactions

The interactions come from three places: CYP2D6 metabolism of xanomeline, renal tubular secretion of trospium, and the anticholinergic effects of trospium on the gut and other organs. None of the label's interactions carries a mandatory dose change; each says to monitor.

Bupropion is a strong CYP2D6 inhibitor that patients with schizophrenia may be taking for depression or smoking cessation, and the label tells you to monitor for more frequent or more severe adverse reactions when the two are combined. The psycho.farm bupropion guide makes the same point. Fluoxetine and paroxetine are the other strong 2D6 inhibitors you will meet in psychiatric patients; paroxetine is also anticholinergic. Sertraline at 150 mg or more and duloxetine inhibit CYP2D6 moderately, and a slower titration is reasonable with them too.

Inducers. The label has no CYP inducer warning and no interaction study with one. Carbamazepine induces CYP1A2, 2C9, 2C19 and 2B6, four of xanomeline's pathways. Treat the combination as unstudied and watch for loss of effect.

Part 9: Special Populations

Pregnancy

There are no human pregnancy data. In rats and rabbits, adverse fetal and neonatal effects (lower fetal and pup weight, stillbirths, neonatal deaths) appeared only at doses toxic to the mother, and no malformations were seen. Untreated schizophrenia carries its own risks, including relapse, hospitalization, suicide and preterm birth.

• Framework: for a patient planning pregnancy, consider an antipsychotic that has human pregnancy data, since this one has none (practice judgment). A patient who becomes pregnant while stable on xanomeline-trospium needs an individual decision, weighing the lack of data against the risk of relapse with a switch.
• The label encourages advising pregnant patients to register with the pregnancy exposure registry it lists (1-866-961-2388).

Lactation

There are no data on xanomeline or trospium in human milk or on effects in the breastfed infant. Both are present in animal milk. The label asks you to weigh the benefits of breastfeeding against the mother's need for the drug and any possible effect on the infant.

Elderly

• The controlled trials enrolled nobody over 65.
• Start at 50 mg/20 mg twice daily, titrate more slowly, and stop at 100 mg/20 mg twice daily. Trospium exposure is 60% higher in this age group.
• Urinary retention risk is highest here, particularly in older men with BPH, and anticholinergic CNS effects may be more likely.
• It is not approved for dementia-related psychosis, and the trials in Alzheimer's psychosis have not reported.

Renal Impairment

• Mild (eGFR 60 to <90 mL/min): usual dose. Exposure is higher, but safety in the trials matched normal function.
• Moderate or severe (eGFR <60 mL/min): not recommended.

Hepatic Impairment

• Mild (Child-Pugh A): not recommended.
• Moderate (B) or severe (C): contraindicated.

Pediatric / Adolescent

Safety and effectiveness have not been established. Any use under 18 is off-label and without trial data.

Part 10: Discontinuation and Taper

The label describes no discontinuation syndrome and gives no taper schedule. With half-lives of 5 to 6 hours, both components are largely gone within a day or two of the last dose.

• Relapse risk: no randomized withdrawal data exist yet for this drug; the maintenance trial began in 2026. Stopping it in a stable patient means losing antipsychotic coverage within days, so plan the next drug before you stop.
• Switching away: The two-week cross-taper (Part 4) applies in this direction too, as practice. Start the new antipsychotic before you stop xanomeline-trospium.
• Stopping for side effects: GI, heart rate and anticholinergic effects should fade as the drug clears. Urinary retention or liver injury may need treatment of its own.
• Angioedema or substantial liver injury: stop at once.

Part 11: Xanomeline-Trospium vs the Alternatives

Payers often place it behind the generics. One state Medicaid plan's 2025 criteria require failure of, intolerance of, or a contraindication to at least three formulary atypicals (aripiprazole, olanzapine, quetiapine, risperidone or ziprasidone) and a psychotic exacerbation within the past two months before approval, with a limit of 60 capsules per 30 days.

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