What If Clozapine Doesn't Work? The Evidence on ECT, Aripiprazole, and Other Add-Ons

Creator: Ryan S. Sultan, MD
Published: 2026-11-12

By Ryan S. Sultan, MD
Psychiatrist · Columbia University Irving Medical Center
Published November 12, 2026 · 5-minute read

In pooled trial data, 40.1% of people with treatment-resistant schizophrenia met response criteria on clozapine.¹ A 2017 overview of the meta-analytic literature found that no combination strategy with clozapine outperformed controls.²

An international expert survey reached consensus on two add-ons for persistent positive symptoms: a second antipsychotic (amisulpride or oral aripiprazole) and electroconvulsive therapy (ECT).³ The trial evidence behind each is mixed.

The first step is confirming the clozapine trial was adequate

In the same survey, experts agreed at 75% or more on raising the clozapine plasma level to at least 350 ng/mL for refractory positive, negative, and mixed symptoms. That figure is expert agreement, and the authors noted that randomized evidence for clozapine-resistant schizophrenia is limited.³

A 2016 meta-analysis concluded that if there's no response by 6 months, medications with fewer adverse reactions should be considered.⁴ For negative symptoms, the experts recommended waiting for a delayed response.³

Dose, level, and medication changes are made with the prescriber. The criteria for an adequate trial are on the page about when to start clozapine.

ECT added to clozapine: a positive trial and a negative sham-controlled trial

A 2015 trial randomized 39 people with clozapine-resistant schizophrenia to 8 weeks of bilateral ECT plus clozapine or to clozapine as usual. In the ECT group, 50% met the response criterion, and no one in the clozapine group did. The study was single-blind, and the comparison group received no sham procedure.⁵

A 2024 double-blind trial compared 20 sessions of ECT with sham ECT in 40 outpatients whose baseline clozapine levels were at least 350 ng/mL. At the end, 1 of 19 completers in the ECT group and 0 of 17 in the sham group had a 50% or greater reduction in total symptom score. The authors found no evidence that ECT was better than sham.⁶

A 2026 meta-analysis pooled three randomized trials with 102 participants, two of them sham-controlled. ECT increased response on the primary outcome (risk ratio 5.63; 95% CI, 1.00 to 31.57). The authors attributed that result to one large-effect study without sham ECT, and the sham-controlled studies showed no significant benefit.⁷

An earlier meta-analysis of 18 randomized trials with 1,769 participants reported response in 53.6% with ECT and 25.4% without. Patient-reported memory impairment occurred in 24.2% compared with 0%, and headache in 14.5% compared with 1.6%.⁸ A 2019 Cochrane review of ECT in treatment-resistant schizophrenia more broadly rated 14 of 15 studies at high risk of bias related to blinding.⁹

Durability is uncertain. In a 2016 review, 20 of 62 patients with follow-up data (32%) relapsed after ECT stopped.¹⁰

Adding aripiprazole: register data favor a medium dose

A 2025 study followed people taking clozapine in Finnish (N=14,053) and Swedish (N=8,743) national registers. One add-on was associated with a lower risk of hospitalization for psychosis in both countries: aripiprazole at 9 to under 16.5 mg/day combined with clozapine at 330 mg/day or more. The adjusted hazard ratio was 0.68 (95% CI, 0.62 to 0.75) compared with clozapine alone.¹¹

Higher doses of aripiprazole, and high doses of the other add-on antipsychotics studied, were associated with an increased risk of hospitalization.¹¹

These are observational data comparing periods on and off the combination within the same individuals. The outcome was hospitalization, and the results cannot establish that aripiprazole caused the difference.¹¹

What randomized trials of add-on medications show

In a 2006 placebo-controlled trial, 6 of 34 who had risperidone added to clozapine responded, compared with 9 of 34 who had placebo added (P=0.38).¹² A 2023 network meta-analysis of 35 trials with 1,472 patients found that add-on antipsychotics, as a group, were not associated with more efficacy than placebo.¹³

A 2018 meta-analysis of 46 studies of 25 interventions found the most support for aripiprazole, fluoxetine, and sodium valproate for total symptoms and memantine for negative symptoms. Its authors tempered that conclusion because of short follow-up and poor study quality.¹⁴

Antidepressants reached expert consensus for clozapine-refractory negative symptoms.³ In a 2025 register study of 23,206 clozapine users, sertraline was associated with the lowest relapse risk (adjusted hazard ratio 0.76). That finding is also observational.¹⁵

CBT: the FOCUS trial was negative on its primary outcome

The FOCUS trial randomized 487 people who hadn't responded to clozapine or couldn't tolerate it to cognitive behavioral therapy plus usual treatment or usual treatment alone. Therapy was up to 30 hours over 9 months.^{16, 17} The PANSS total score at 21 months, the primary outcome, did not differ (mean difference -0.89 points; p=0.48). At 9 months the CBT group was 2.40 points better, which the authors called statistically, though not clinically, significant.¹⁶

The authors concluded that the results don't support routinely offering CBT to everyone with clozapine-resistant schizophrenia, and that an individual trial might be indicated for some.¹⁶ A meta-analysis of four studies found no significant change in total psychotic symptoms and a small improvement in positive symptoms at the end of therapy (standardized mean difference -0.33).¹⁸

Limitations of the evidence

This evidence has limitations. First, the positive ECT trial had no sham control, and the sham-controlled trial that followed was negative. Second, the aripiprazole and antidepressant findings are observational, and the randomized augmentation trials were short and often of poor quality. Nevertheless, expert consensus and the register data suggest a sequence to work through with the prescriber: confirm the level and the duration of the clozapine trial, then weigh medium-dose aripiprazole or ECT with a clear view of what each has and hasn't shown.

Frequently asked questions

What happens if clozapine doesn't work?

In pooled trial data, 40.1% of people with treatment-resistant schizophrenia met response criteria on clozapine. For the others, an expert survey reached consensus on raising the clozapine level to at least 350 ng/mL, and on adding a second antipsychotic or ECT for persistent positive symptoms. Those decisions are made with the prescriber.^{1, 3}

Does ECT work when clozapine fails?

The evidence is mixed. In a 39-person trial without a sham control, 50% of the ECT group met the response criterion and no one in the clozapine group did. A 2024 sham-controlled trial of 40 outpatients found no evidence that ECT was better than sham.^{5, 6}

Can you add Abilify (aripiprazole) to clozapine?

In Finnish and Swedish register data, aripiprazole at 9 to under 16.5 mg/day added to clozapine at 330 mg/day or more was associated with a lower risk of hospitalization for psychosis, with an adjusted hazard ratio of 0.68. Higher doses of aripiprazole were associated with an increased risk. The data are observational, and adding or changing a medication is a decision for the prescriber.¹¹

Does ECT with clozapine cause memory loss?

In a meta-analysis of 18 randomized trials, patient-reported memory impairment occurred in 24.2% of people who had ECT added to clozapine compared with 0% of those who did not.⁸

Does therapy help if clozapine is not working?

In the FOCUS trial of 487 people, CBT did not improve total symptom scores at 21 months, the primary outcome. The authors concluded that the results don't support routinely offering CBT to everyone with clozapine-resistant schizophrenia, and that an individual trial might be indicated for some.¹⁶

In a crisis: call or text 988, or go to the nearest emergency department. A first episode of psychosis belongs in a hospital-based or coordinated specialty care program.

I start and manage clozapine in an outpatient practice in Chelsea, Manhattan. Details are on the schizophrenia care in NYC page. Clozapine should not be stopped, skipped, or restarted without the prescriber. This page is general information and does not replace an evaluation.