Sinequan (Doxepin) Drug Information: Clinical Pharmacology

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May 27, 2012

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Antidepressants are a class of drugs that reduce symptoms of depressive disorders by correcting chemical imbalances of neurotransmitters in the brain. Chemical imbalances may be responsible for changes in mood and behavior.

Neurotransmitters are vital, as they are the communication link between nerve cells in the brain. Neurotransmitters reside within vesicles found in nerve cells, which are released by one nerve and taken up by other nerves. Neurotransmitters not taken up by other nerves are taken up by the same nerves that released them. This process is called "reuptake." The prevalent neurotransmitters in the brain specific to depression are serotonin, dopamine and norepinephrine (also called noradrenaline).

In general, antidepressants work by inhibiting the reuptake of specific neurotransmitters, hence increasing their levels around the nerves within the brain, such...

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CLINICAL PHARMACOLOGY

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The mechanism of action of SINEQUAN (doxepin HCl) is not definitely known. It is not a central nervous system stimulant nor a monoamine oxidase inhibitor. The current hypothesis is that the clinical effects are due, at least in part, to influences on the adrenergic activity at the synapses so that deactivation of norepinephrine by reuptake into the nerve terminals is prevented. Animal studies suggest that doxepin HCl does not appreciably antagonize the antihypertensive action of guanethidine. In animal studies anticholinergic, antiserotonin and antihistamine effects on smooth muscle have been demonstrated. At higher than usual clinical doses, norepinephrine response was potentiated in animals. This effect was not demonstrated in humans.

At clinical dosages up to 150 mg per day, SINEQUAN (doxepin) can be given to man concomitantly with guanethidine and related compounds without blocking the antihypertensive effect. At dosages above 150 mg per day blocking of the antihypertensive effect of these compounds has been reported.

SINEQUAN (doxepin) is virtually devoid of euphoria as a side effect. Characteristic of this type of compound, SINEQUAN (doxepin) has not been demonstrated to produce the physical tolerance or psychological dependence associated with addictive compounds.

Last reviewed on RxList: 8/29/2007
This monograph has been modified to include the generic and brand name in many instances.