11-(3-(Dimethylamino) propylidene)-6H-dibenz(b,e)oxepine

Absorption
T max is 2 to 8 days (steady-state).

Metabolism
Metabolized in the liver to desmethyldoxepin (active).

Elimination
Urinary excretion; t ½ is 8 to 24 h (oral), 28 to 52 h (topical).

Alcohol/CNS depressants
CNS and respiratory depression may be potentiated.

Cimetidine
May inhibit metabolism of doxepin, leading to increased concentrations.

Clonidine
Concurrent use may lead to loss of BP control and possibly dangerous increases in BP.

Guanethidine
Hypotensive action may be inhibited.

MAOIs
Concurrent use may lead to severe seizures, hyperpyretic crisis, and fatal reactions. Generally, allow 7 to 10 days between discontinuation of 1 drug and start of another.

SSRIs (eg, fluoxetine)
May increase serum concentrations of doxepin; effect may occur up to 5 wk after discontinuation of fluoxetine.

Sympathomimetics (eg, dopamine, epinephrine)
Pressor response may increase or decrease; arrhythmias may occur.

Type IC antiarrhythmics (eg, propafenone, flecainide)
May inhibit metabolism of doxepin, leading to increased concentrations.