"Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as the sensation of itch.
Controlled Clinical Trials
Systemic Adverse Effects: In controlled clinical trials of patients treated with Doxepin HCl Cream 5%, the most common systemic adverse effect reported was drowsiness. Drowsiness occurred in 22% of patients treated with Doxepin HCl Cream 5% (and 2% of patients treated with placebo cream) and resulted in the premature discontinuation of the drug in approximately 5% of patients treated.
Local Site Adverse Effects: In controlled clinical trials of patients treated with Doxepin HCl Cream 5%, the most common local site adverse effect reported was burning and/or stinging at the site of application. These occurred in approximately 21% of these patients. Most of these reactions were categorized as "mild"; however, approximately 25% of patients who reported burning and/or stinging reported the reaction as "severe". Four patients treated with Doxepin HCl Cream 5% withdrew from the study because of the burning and/or stinging.
Other local site adverse effects reported in approximately 1 to 10% of these patients included: Pruritus exacerbation, eczema exacerbation, dryness and tightness to skin, paresthesias, and edema.
Other local site adverse effects reported in less than 1% of these patients included: Irritation, tingling, scaling, and cracking.
Post Marketing Experience
Some cases of allergic contact dermatitis have been reported in patients using Doxepin HCl 5% cream.
Read the Prudoxin (doxepin) Side Effects Center for a complete guide to possible side effects
Studies have not been performed examining drug interactions with PRUDOXIN (doxepin) Cream. However, data are available regarding potentially significant drug interactions regarding doxepin. As plasma levels of doxepin similar to therapeutic ranges for antidepressant therapy can be obtained following topical application of PRUDOXIN (doxepin) Cream, it would not be unexpected for the following drug interactions to be possible following topical PRUDOXIN (doxepin) Cream application.
MAO Inhibitors: Serious side effects and even death have been reported following the concomitant use of certain orally administered drugs chemically related to doxepin and MAO inhibitors. Therefore, MAO inhibitors should be discontinued at least two weeks prior to the initiation of treatment with PRUDOXIN (doxepin) Cream.
Cimetidine: Cimetidine has been reported to produce clinically significant fluctuations in steady-state serum concentrations of various tricyclic antidepressants. Serious anticholinergic symptoms have been associated with elevations in the serum levels of tricyclic antidepressants when cimetidine therapy is initiated. Additionally, higher than expected tricyclic antidepressant levels have been observed in patients already taking cimetidine. In patients who have been reported to be well-controlled on tricyclic antidepressants receiving concurrent cimetidine therapy, discontinuation of cimetidine has been reported to decrease established steady-state serum tricyclic antidepressant levels and compromise their therapeutic effects.
Alcohol: Alcohol ingestion may exacerbate the potential sedative effects of PRUDOXIN (doxepin) Cream.
Drugs Metabolized by P450IID6: A subset (3% to 10%) of the population has reduced activity of certain drug metabolizing enzymes such as the cytochrome P450 isozyme P450IID6. Such individuals are referred to as "poor metabolizers" of drugs such as debrisoquin, dextromethorphan, and the tricyclic antidepressants. These individuals may have higher than expected plasma concentrations of tricyclic antidepressant when given usual doses. In addition, certain drugs that are metabolized by this isozyme, including many antidepressants (tricyclic antidepressants, selective serotonin reuptake inhibitors, and others), may inhibit the activity of this isozyme, and thus may make normal metabolizers resemble poor metabolizers with regard to concomitant therapy with other drugs metabolized by this enzyme system, leading to drug interactions.
Concomitant use of tricyclic antidepressants with other drugs metabolized by cytochrome P450IID6 may require lower doses than usually prescribed for either the tricyclic antidepressant or the other drug. Therefore, co-administration of tricyclic antidepressants with other drugs that are metabolized by this isoenzyme, including other antidepressants, phenothiazines, carbamazepine, and Type 1C antiarrhythmics (e.g., propafenone, flecainide and encainide), or that inhibit this enzyme (e.g., quinidine), should be approached with caution. Concomitant use of PRUDOXIN (doxepin) Cream with drugs metabolized by cytochrome P450IID6 has not been formally studied.
Last reviewed on RxList: 11/21/2008
This monograph has been modified to include the generic and brand name in many instances.
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