Cimetidine and Risperidone Interaction
Drug interaction information between Cimetidine and Risperidone.
Cimetidine and Risperidone have a documented major interaction in FDA labeling.
FDA drug labeling documents a major-severity interaction between Cimetidine and Risperidone. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Cimetidine can slightly slow down the enzymes that break down risperidone, but the effect is very small.
What To Do
No dose changes are needed when taking these two medicines together.
FDA Label Information
Dose adjustment is not recommended for risperidone tablets when co-administered with ranitidine, cimetidine, amitriptyline, or erythromycin [see Table 18 ] . Do not exceed twice the patient’s usual dose Enzyme (CYP3A) inhibitors Ranitidine 150 mg twice daily 1 mg single dose 1.2 1.4 Dose adjustment not needed Cimetidine 400 mg twice daily 1 mg single dose 1.1 1.3 Dose adjustment not needed Erythromycin 500 mg four times daily 1 mg single dose 1.1 0.94 Dose adjustment not needed Other Drugs Amitriptyline 50 mg twice daily 3 mg twice daily 1.2 1.1 Dose adjustment not Needed *Change relative...
Cimetidine Also Interacts With
- Levofloxacin major
- Posaconazole major
- Valproate major
- Empagliflozin moderate
- Empagliflozin/Linagliptin moderate
Risperidone Also Interacts With
- Amitriptyline major
- Carbamazepine major
- Lithium major
- Erythromycin major
- Ranitidine major
Frequently Asked Questions
Can I take Cimetidine and Risperidone together?
This is a major interaction. No dose changes are needed when taking these two medicines together.
How serious is the interaction between Cimetidine and Risperidone?
This interaction is classified as "major" severity by the FDA. Major interactions may be life-threatening or cause serious side effects.
Why do Cimetidine and Risperidone interact?
Cimetidine can slightly slow down the enzymes that break down risperidone, but the effect is very small.
Understanding the Cimetidine and Risperidone Interaction
FDA-approved prescribing information for these two drugs flags their combination as a major-severity interaction. Cimetidine belongs to the H2 Receptor Antagonist class and Risperidone belongs to the Atypical Antipsychotic class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Cimetidine can slightly slow down the enzymes that break down risperidone, but the effect is very small. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Cimetidine has 77 total documented interactions on file in this dataset, and Risperidone has 20. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: No dose changes are needed when taking these two medicines together. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Cimetidine or Risperidone based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.