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Doxepin Hydrochloride topical

Pronunciation

Class: Antipruritics and Local Anesthetics
ATC Class: N06AA12
VA Class: CN601
Chemical Name: 3-Dibenz[b, e]oxepin-11(6H)ylidene-N, N-dimethyl-1-propanamine hydrochloride
Molecular Formula: C19H21NO
CAS Number: 1668-19-5
Brands: Prudoxin, Zonalon

Introduction

Antipruritic agent; dibenzoxepin-derivative tricyclic antidepressant compound with antihistaminic activity.1 2 4 5 6 b c

Uses for Doxepin Hydrochloride

Dermatologic Conditions

Used for short-term (up to 8 days) relief of moderate pruritus associated with various forms of eczematous dermatitis, including atopic dermatitis and lichen simplex chronicus (circumscribed or localized neurodermatitis).1 2 b c

Doxepin Hydrochloride Dosage and Administration

Administration

Topical Administration

Apply topically to the skin as a 5% cream.1 2 b c

For external use only;1 c should not be used near or in eyes, orally, or intravaginally.1 b c

Do not use with occlusive dressings (e.g., bandaged or otherwise covered or wrapped).3 b c (See Occlusive Dressings under Cautions.)

Dosage

Available as doxepin hydrochloride; dosage expressed in terms of the salt.b c

Adults

Dermatologic Conditions
Topical

Apply a thin film to affected area(s) of the skin 4 times daily, with an interval of at least 3–4 hours between applications, for up to 8 days.1 b c d

Prescribing Limits

Adults

Dermatologic Conditions
Topical

Safety and efficacy of >8 days of therapy not established.1 b c

Special Populations

Geriatric Patients

Select dosage with caution, generally start at low end of dosing range, due to possible age-related decrease in hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.b

Cautions for Doxepin Hydrochloride

Contraindications

  • Untreated narrow angle glaucoma.b d

  • Urinary retention.b d

  • Known sensitivity to doxepin or any ingredient in the formulation.b d

Warnings/Precautions

Warnings

CNS Effects

Drowsiness reported in >20% of patients following topical application, especially when applied to >10% of body surface area.1 b c d

Performance of activities requiring mental alertness and physical coordination may be impaired.b c

Concurrent use of other CNS depressants may cause additive or potentiated CNS depression.b c (See Specific Drugs under Interactions.)

If excessive drowsiness occurs, reduce number of daily applications, the amount of cream applied, and/or the percentage of body surface area treated, or discontinue the drug.1 b c Efficacy of cream with reduced frequency applications not established.b

Sensitivity Reactions

Hypersensitivity Reactions

Hypersensitivity reactions, including allergic contact dermatitis reported.b c

General Precautions

Occlusive Dressings

Possible increased absorption; avoid occlusive dressings.b c

Specific Populations

Pregnancy

Category B.b c

Lactation

Not known whether topical doxepin is distributed into milk, but systemic exposure may occur after topical administration.b c Distributed into milk following oral administration.b c Discontinue nursing or the drug.b c

Pediatric Use

Safety and efficacy of topical doxepin not established.1 b c Manufacturer does not recommend topical doxepin in pediatric patients.b

Somnolence, grand mal seizure, respiratory depression, ECG abnormalities, and coma reported in a 2.5 year old pediatric patient following topical doxepin administration (27 grams) over 3 days.b

Geriatric Use

Clinical studies did not include sufficient numbers of subjects ≥65 years of age to determine whether they respond differently from younger subjects.b

May cause confusion and oversedation in geriatric patients;b observe geriatric patients closely following doxepin cream administration.b

Common Adverse Effects

Drowsiness,b c burning,d dry mouth,b c dry lips,b c thirst.b c

Interactions for Doxepin Hydrochloride

No interactions identified to date when topical doxepin used concomitantly with other topical or systemic drugs.b c Because clinically relevant systemic absorption may occur following topical application, drug interactions between topical doxepin and systemically administered drugs may occur.b c (See Absorption under Pharmacokinetics.)

Metabolized in the liver by various CYP isoenzymes (e.g., CYP2D6, CYP1A2, CYP3A4).e

Drugs Metabolized by Hepatic Microsomal Enzymes

Inhibitors and substrates of CYP2D6; potential pharmacokinetic interaction (increased plasma doxepin concentrations). Consider possible interactions related to TCA class of drugs.b c

Specific Drugs

Drug

Interaction

Comments

Alcohol

May potentiate sedative effects1 b c

Use concomitantly with cautionb

Antiarrhythmics: class 1C (propafenone, flecainide); quinidine

Possible increased plasma doxepin concentrationsc

Monitor for TCA toxicityb

Use concomitantly with caution;b c decreased doxepin dosage may be requiredc

Antidepressants, tricyclics (TCAs)

May potentiate sedative effectsb

Use concomitantly with caution;b may require lower doses and monitoring of TCA concentrations1 b c

Antihistamines

May potentiate sedative effectsb

Carbamazepine

Possible increased plasma doxepin concentrationsc

Use concomitantly with cautionc

Cimetidine

Possible increased plasma doxepin concentrationsb c

Potential for tricyclic toxicity, particularly anticholinergic adverse effectsb c

MAO inhibitors

Potentially life-threatening serotonin syndromeb c e

Discontinue MAO inhibitor ≥2 weeks prior to cautious initiation of doxepin creamb c

Phenothiazines

Possible increased plasma doxepin concentrationsc

Use concomitantly with cautionc

SSRIs (e.g., fluoxetine, paroxetine, sertraline)

Possible increased plasma doxepin concentrationsc

Use with caution; monitor for TCA toxicityb c

Discontinue fluoxetine ≥5 weeks prior to initiating doxepinb

Tolazamide

Severe hypoglycemia reported in a diabetic patient receiving oral doxepinb

Doxepin Hydrochloride Pharmacokinetics

Absorption

Bioavailability

Absorbed percutaneously into systemic circulation following topical application.1 b c Plasma concentrations following topical application may be similar to those occurring following oral administration.b d

Percutaneous penetration can be increased by use of occlusive dressings.b c

Onset

Following topical application, antipruritic effects may occur within 15 minutes.d

Distribution

Extent

Widely distributed in body tissues including lungs, heart, brain, and liver.b

Not known whether topical doxepin is distributed into milk; distributed into milk following oral administration.b c

Elimination

Metabolism

Extensively metabolized in the liver by various CYP isoenzymes (principally CYP2D6); undergoes demethylation to pharmacologically active metabolite, desmethyldoxepin.b e

Elimination Route

Excreted in urine following glucuronidation as unchanged drug and metabolites.b

Half-life

Half-life of desmethyldoxepin ranges from 28 to 52 hours and is not affected by multiple dosing.b

Special Populations

Renal disease, genetic factors, age, and other medications may affect the metabolism and subsequent elimination of doxepin.b

Stability

Storage

Topical

Cream

≤27°C.b c

Actions

  • Exact mechanism of antipruritic activity is unknown; appears to exhibit potent histamine H1- and H2-receptor antagonist activity.1 2 4 5 6 b d

  • Sedative effect may contribute to antipruritic activity;1 b however, antipruritic efficacy does not appear to depend on sedative effect.2 3

Advice to Patients

  • Importance of using only as directed, only for the disorder for which it was prescribed, and for no longer than prescribed; avoid contact with the eyes and only apply externally as directed.c d

  • Importance of avoiding use of occlusive dressings.3 b c

  • Risk of drowsiness, especially if doxepin cream is applied to >10% of body surface area.1 b c d

  • Importance of considering possible impaired ability to perform hazardous activities (e.g., operating hazardous machinery, driving a motor vehicle).b c

  • Inform patients that their response to alcohol may be increased.b c

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.b c

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.d

  • Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Doxepin Hydrochloride

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Topical

Cream

5% (4.43% of doxepin)

Prudoxin

Healthpoint

Zonalon

Doak

AHFS DI Essentials. © Copyright, 2016, American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814. Review Date: September 06, 2016.

References

1. GenDerm Corporation. Zonalon (doxepin hydrochloride) cream 5% prescribing information. Lincolnshire, IL: 1994 Jan.

2. GenDerm Corporation. Zonalon (doxepin hydrochloride cream), 5%: a clinical review. (Publication No. G0079) Lincolnshire, IL: 1994 Mar.

3. GenDerm, Lincolnshire, IL: Personal communication.

4. Sullivan TJ. Pharmacologic modulation of the whealing response to histamine in human skin: identification of doxepin as a potent in vivo inhibitor. J Allergy Clin Immunol. 1982; 69:260-7. [IDIS 157885] [PubMed 6120966]

5. Bernstein JE, Whitney DH, Soltani K. Inhibition of histamine-induced pruritus by topical tricyclic antidepressants. J Am Acad Dermatol. 1981; 5:582-5. [PubMed 7298924]

6. Richelson E. Tricyclic antidepressants and histamine H1 receptors. Mayo Clin Proc. 1979; 54:669-74. [PubMed 39202]

a. AHFS Drug Information 2007. McEvoy GK, ed. Doxepin . Bethesda, MD: American Society of Health-System Pharmacists; 2007: 3537.

b. Doak Dermatologics. Zonalon (doxepin hydrochloride) 5% cream prescribing information. Fairfield, NJ; 2005 May.

c. Healthpoint. Prudoxin (doxepin hydrochloride) 5% cream prescribing information. Fort Worth, TX; Undated.

d. Healthpoint. Prudoxin (doxepin hydrochloride) 5% cream patient information. Fort Worth, TX; Undated.

e. AHFS Drug Information 2008. McEvoy GK, ed. Tricyclic antidepressants general statement . Bethesda, MD: American Society of Health-System Pharmacists; 2008:

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