DOXEPIN HCL

Chemistry - A dibenzoxazepine derivative tricyclic antidepressant, doxepin HCl occurs as a white powder that is freely soluble in alcohol.

Storage, Stability, Compatibility

Store products in protected from direct sunlight in tight, light-resistant containers at room temperature.

Pharmacology - DOXEPIN HCL

Doxepin is a tricyclic agent that has a antihistaminic, anticholinergic, and alpha-adrenergic blocking activity. In the CNS, doxepin inhibits the reuptake of norepinephrine and serotonin (5-HT) by the presynaptic neuronal membrane, thereby increasing their synapticconcentrations. Doxepin is considered to be a moderate inhibitor of norepinephrine and weakinhibitor of serotonin.
Uses, Indications - The primary use for doxepin in veterinary medicine is the adjunctive therapy ofpsychogenic dermatoses, particularly those that have an anxiety component.

Pharmacokinetics - DOXEPIN HCL

Doxepin appears to be well absorbed after oral administration. Doxepin andits N-demethylated active metabolite are distributed into milk. The drug is extensively metabolizedin the liver.

Contraindications, Precautions, Reproductive Safety

These agents are contraindicated if priorsensitivity has been noted with any other tricyclic. Concomitant use with monoamine oxidaseinhibitors is generally contraindicated. Doxepin is probably contraindicated in dogs with urinaryretention or glaucoma.
Rodent studies have demonstrated no teratogenic effects, but safety during pregnancy has not beenestablished. Doxepin is excreted into milk, and one case report of sedation and respiratorydepression in the infant has been reported.

Adverse Effects, Warnings

While doxepin has less potential for cardiac adverse effects thanmany other tricyclics, it can cause ventricular arrhythmias, particularly after overdoses. In dogs, itmay also cause hyperexcitability, GI distress, or lethargy. However, potential adverse effects can runthe entire gamut of systems. Refer to other human drug references for additional information.
Overdosage, Acute Toxicity - Overdosage with tricyclics can be life-threatening (arrhythmias, cardiorespiratory collapse). Because the toxicities and therapies for treatment are complicated andcontroversial, it is recommended to contact an animal poison control center for further informationin any potential overdose situation.

Drug Interactions

Because of additive effects, use doxepin cautiously with other agents with anticholinergic or CNS depressant effects. Tricyclic antidepressants used with antithyroid agents may increase the potential risk of agranulocytosis. Cimetidine may inhibit tricyclic antidepressant metabolism and increase the risk of toxicity. Use in combination with sympathomimetic agents may increase the risk of cardiac effects (arrhythmias, hypertension, hyperpyrexia). Concomitant use with monoamine oxidase inhibitors is generally contraindicated.
Laboratory Considerations - Tricyclics can widen QRS complexes, prolong PR intervals and invert or flatten T-waves on ECG. Tricyclics may alter (increase or decrease) blood glucose levels.