Clozapine Plasma Concentration Calculator and Interpreter

This educational tool estimates steady‑state (at least 5-7 days of consistent dosing) 12-hour trough concentrations (ng/mL) from published nomograms and typical interaction effects. Real patients can vary substantially (~±30%) due to sampling time, adherence, labs, and biology; confirm with therapeutic drug monitoring and clinical judgment.

Instructions for Proper Use

1. Maintain a consistent dose for at least 5-7 days. Typically clinicians choose a round number such as 100 mg (total daily dose) before getting a level, for ease of calculations, but this should help with that.
2. Enter the patient’s total dose, sex, age, weight in kg, smoking status, presence of valproate and inhibitors or inducers.
3. Make any adjustments to the dosage.
4. Wait another 5-7 days and obtain a blood level.
5. Enter the results of the ACTUAL blood level at the bottom of the calculator and receive feedback as to the discrepancy.
6. Click “copy summary” to copy into the medical record.

The calculator was developed by Bruce Bassi MD, an inpatient and outpatient psychiatrist who regularly uses clozapine in his practice. The calculator was created with the use of AI and the references cited below. You are welcome to submit feedback.