Drug Interaction Report

MONITOR: Coadministration of fluoxetine with calcium channel blockers may increase their plasma concentrations and the risk of side effects. The mechanism is reduced clearance of the calcium channel blocker due to inhibition of CYP450 3A4-mediated metabolism by fluoxetine. Reports exist for nifedipine, nimodipine, and verapamil. Theoretically, the interaction may also occur with other calcium channel blockers that are CYP450 3A4 substrates.

MANAGEMENT: Monitoring of clinical response and tolerance, including blood pressure, is recommended if fluoxetine is used in combination with calcium channel blockers that are metabolized by CYP450 3A4. Dose reductions may be considered, if necessary. Patients should be advised to seek medical attention if they experience edema or swelling of the lower extremities; sudden, unexplained weight gain; difficulty breathing; chest pain or tightness; or hypotension as indicated by dizziness, fainting, or orthostasis.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.