Drug Interactions between mitotane and Poly-Tussin AC

MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring 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.

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MONITOR: Coadministration of codeine with potent or moderate CYP450 3A4 inducers may result in lower codeine plasma concentrations, higher levels of the inactive metabolite norcodeine, and less metabolism via CYP450 2D6, resulting in lower morphine levels. This interaction may lead to reduced codeine efficacy and potentially initiate the onset of withdrawal symptoms in patients who are physically dependent. In addition, patients may be at an increased risk of CNS and/or respiratory-depressant effects from increased levels of codeine once concomitant therapy with the CYP450 3A4 inducer is ceased. This is particularly worrisome if the CYP450 3A4 inducer also possesses CNS- and/or respiratory-depressant effects. This interaction has also been reported with dihydrocodeine.

MANAGEMENT: The potential loss of efficacy of codeine or dihydrocodeine and onset of opioid withdrawal symptoms should be considered when used in combination with a potent or moderate CYP450 3A4 inducer. Alternative agents with no or minimal CYP450 3A4 induction potential are recommended whenever possible. Some manufacturers of products containing codeine advise against the concomitant use of codeine with CYP450 3A4 inducers. If concomitant use is considered necessary, caution and close clinical and laboratory monitoring are recommended. Dosage adjustments may also be required whenever a CYP450 3A4 inducer is added to or withdrawn from therapy. Following discontinuation of a CYP450 3A4 inducer, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression.

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MONITOR: Coadministration with alcohol or other central nervous system (CNS) depressants may enhance the sedative effects of mitotane and increase the likelihood and/or severity of central nervous system (CNS) side effects. In clinical studies and post marketing reports, CNS side effects occurred in 40% of patients, primarily consisting of depression as manifested by lethargy and somnolence (25%), and dizziness or vertigo (15%). Mitotane plasma concentrations exceeding 20 mcg/mL are associated with a greater incidence of severe neurologic toxicity. Clinical data are not available for the concomitant use of mitotane with other CNS depressants.

MANAGEMENT: Caution and clinical monitoring for increased CNS adverse effects is advised if mitotane is coadministered with alcohol, other CNS depressants, or agents that cause dizziness or vertigo. Patients should not drive, operate machinery, or engage in hazardous activities requiring mental alertness and motor coordination until they know how the medications affect them. In addition, more frequent monitoring of serum mitotane levels may be considered.

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