Interactions

Drug-Drug

• Amitriptyline is metabolized in the liver by the cytochrome P450 2D6 enzyme, and its action may be affected by drugs that compete for metabolism by this enzyme, including other antidepressants, phenothiazines, carbamazepine, class 1C antiarrhythmics including propafenone, and flecainide; when these drugs are used concurrently with amitriptyline, dosage of one or the other or both may be necessary. Concurrent use of other drugs that inhibit the activity of the enzyme, including cimetidine, quinidine, amiodarone, and ritonavir, may result in effects of amitriptyline

• May cause hypotension, tachycardia, and potentially fatal reactions when used with MAO inhibitors (avoid concurrent use—discontinue 2 wk before starting amitriptyline)

• Concurrent use with SSRI antidepressants may result in toxicity and should be avoided (fluoxetine should be stopped 5 wk before starting amitriptyline)

• Concurrent use with clonidine may result in hypertensive crisis and should be avoided

• Concurrent use with levodopa may result in delayed or absorption of levodopa or hypertension

• Blood levels and effects may be by rifamycins (rifampin, rifapentine, and rifabutin)

• Concurrent use with moxifloxacin risk of adverse cardiovascular reactions

• CNS depression with other CNS depressants including alcohol, antihistamines, clonidine, opioids, and sedative/hypnotics

• Barbiturates may alter blood levels and effects

• Adrenergic and anticholinergic side effects may be with other agents having anticholinergic properties

• Phenothiazines or oral contraceptives levels and may cause toxicity

• Nicotine may metabolism and alter effects

• St. John's wort may decrease serum concentrations and efficacy

• Concomitant use of kava-kava, valerian, or chamomile can increase CNS depression

• Increased anticholinergic effects with jimson weed and scopolia

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