The time to peak concentration (Tmax) of doxepin at 6 mg is about 3.5 hours after oral administration in fasting individuals
The Tmax is delayed by approximately an additional 3 hours if doxepin is taken with a high-fat meal.
Thus, it is recommended that doxepin be taken without food, to minimize the risk of next day sedation, given it is possible for the Tmax to be as long as 6 hours after taking it.[1]
Indications
Insomnia (middle insomnia, doses of 3 to 6 mg qHS in Canada)[2]
Best used for the short-term treatment of maintenance (middle) insomnia, not initial insomnia
Mechanism
Doxepin is highly histaminergic and often used as a reference standard in drug comparison studies when looking at histaminergic activity.
Doxepin is the most potent antihistamine of the tricyclic antidepressants, with 4x the potency of amitriptyline and 800x the potency of diphenhydramine at the H1 receptor.[3]
Doxepin has no anticholinergic effects, which makes it a relatively “safe” sleep aid