Ciprofloxacin and Clozapine interaction
Ciprofloxacin and Clozapine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Ciprofloxacin label · effective 2026-06-30
Avoid use in patients with known prolongation, those with hypokalemia, and with other drugs that prolong the QT interval.
Table 8: Drugs That are Affected by and Affecting Ciprofloxacin Drugs That are Affected by Ciprofloxacin Drug(s) Recommendation Comments Tizanidine Contraindicated Concomitant administration of tizanidine and ciprofloxacin is contraindicated due to the potentiation of hypotensive and sedative effects of tizanidine [see Contraindications ( 4.2 )].
Co-administration of ciprofloxacin and other drugs primarily metabolized by CYP1A2 (for example, theophylline, methylxanthines, caffeine, tizanidine, ropinirole, clozapine, olanzapine and zolpidem), results in increased plasma concentrations of the co-administered drug and could lead to clinically significant pharmacodynamic adverse reactions of the co-administered…
Clozapine Use with caution Careful monitoring of clozapine associated adverse reactions and appropriate adjustment of clozapine dosage during and shortly after co-administration with ciprofloxacin are advised.
…syndrome, uncorrected electrolyte imbalance, such as hypokalemia or hypomagnesemia and cardiac disease, such as heart failure, myocardial infarction, or bradycardia), and patients receiving Class IA antiarrhythmic agents (quinidine, procainamide), or Class III antiarrhythmic agents (amiodarone, sotalol), tricyclic antidepressants, macrolides, and antipsychotics.
From the Clozapine (Clozaril) label · effective 2025-06-06
• Concomitant use of Strong CYP1A2 Inhibitors: Reduce CLOZARIL dose to one-third when coadministered with strong CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin, enoxacin).
CYP1A2 Inhibitors Concomitant use of CLOZARIL and CYP1A2 inhibitors can increase plasma levels of clozapine, potentially resulting in adverse reactions.
Reduce the CLOZARIL dose to one-third of the original dose when CLOZARIL is coadministered with strong CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin, or enoxacin).
The CLOZARIL dose should be increased to the original dose when coadministration of strong CYP1A2 inhibitors is discontinued [see Dosage and Administration ( 2.7 ), Clinical Pharmacology ( 12.3 )] .
Moderate or weak CYP1A2 inhibitors include oral contraceptives and caffeine.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.