Doxepin

Description

11 DESCRIPTION Doxepin is available in 3 mg and 6 mg strength tablets for oral administration. Each tablet contains 3.39 mg or 6.78 mg doxepin hydrochloride, USP equivalent to 3 mg and 6 mg of doxepin, respectively. Chemically, doxepin hydrochloride, USP is an (E) and (Z) geometric, isomeric mixture of 1-propanamine, 3-dibenz[ b ,e]oxepin-11(6 H )ylidene- N,N -dimethyl-hydrochloride. It has the following structure: Doxepin hydrochloride USP is a white or almost white crystalline powder, that is freely soluble in water, ethanol and dichloromethane, soluble in chloroform and in methanol. It has a molecular weight of 315.84 and molecular formula of C 19 H 21 NO

What Is Doxepin Used For?

1 INDICATIONS AND USAGE Doxepin tablets are indicated for the treatment of insomnia characterized by difficulty with sleep maintenance. The clinical trials performed in support of efficacy were up to 3 months in duration. Doxepin tablets are indicated for the treatment of insomnia characterized by difficulties with sleep maintenance. ( 1 , 14 )

Dosage and Administration

2 DOSAGE AND ADMINISTRATION The dose of doxepin tablets should be individualized. Initial dose: 6 mg, once daily for adults ( 2.1 ) and 3 mg, once daily for the elderly. ( 2.1 , 2.2 ) Take within 30 minutes of bedtime. Total daily dose should not exceed 6 mg. ( 2.3 ) Should not be taken within 3 hours of a meal. ( 2.3 , 12.3 ) 2.1 Dosing in Adults The recommended dose of doxepin tablets for adults is 6 mg once daily. A 3 mg once daily dose may be appropriate for some patients, if clinically indicated. 2.2 Dosing in the Elderly The recommended starting dose of doxepin tablets in elderly patients (≥65 years old) is 3 mg once daily. The daily dose can be increased to 6 mg, if clinically indicated. 2.3 Administration Doxepin tablets should be taken within 30 minutes of bedtime. To minimize the potential for next day effects, doxepin tablets should not be taken within 3 hours of a meal [ see Clinical Pharmacology (12.3) ]. The total doxepin tablets dose should not exceed 6 mg per day.

Side Effects (Adverse Reactions)

6 ADVERSE REACTIONS The following serious adverse reactions are discussed in greater detail in other sections of labeling: Abnormal thinking and behavioral changes [see Warnings and Precautions (5.2)] . Suicide risk and worsening of depression [ see Warnings and Precautions (5.3) ] . CNS Depressant effects [ see Warnings and Precautions (5.4) ] . The most common treatment-emergent adverse reactions, reported in ≥ 2% of patients treated with doxepin, and more commonly than in patients treated with placebo, were somnolence/sedation, nausea, and upper respiratory tract infection. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Novadoz Pharmaceuticals LLC at 1-855-668-2369 and or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience The pre-marketing development program for doxepin tablets included doxepin HCl exposures in 1017 subjects (580 insomnia patients and 437 healthy subjects) from 12 studies conducted in the United States. 863 of these subjects (580 insomnia patients and 283 healthy subjects) participated in six randomized, placebo-controlled efficacy studies with doxepin doses of 1 mg, 3 mg, and 6 mg for up to 3-months in duration. Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. However, data from the doxepin studies provide the physician with a basis for estimating the relative contributions of drug and non-drug factors to adverse reaction incidence rates in the populations studied. Associated with Discontinuation of Treatment The percentage of subjects discontinuing Phase 1, 2, and 3 trials for an adverse reaction was 0.6% in the placebo group compared to 0.4%, 1.0%, and 0.7% in the doxepin 1 mg, 3 mg, and 6 mg groups, respectively. No reaction that resulted in discontinuation occurred at a rate greater than 0.5%. Adverse Reactions Observed at an Incidence of ≥ 2% in Controlled Trials Table 1 shows the incidence of treatment-emergent adverse reactions from three long-term (28 to 85 days) placebo-controlled studies of doxepin in adult (N=221) and elderly (N=494) subjects with chronic insomnia. Reactions reported by Investigators were classified using a modified MedDRA dictionary of preferred terms for purposes of establishing incidence. The table includes only reactions that occurred in 2% or more of subjects who received doxepin 3 mg or 6 mg in which the incidence in subjects treated with doxepin was greater than the incidence in placebo-treated subjects. Table 1 Incidence (%) of Treatment-Emergent Adverse Reactions in Long-term Placebo-Controlled Clinical Trials System Organ Class Preferred Term* Placebo (N=278) Doxepin 3 mg (N=157) Doxepin 6 mg (N=203) Nervous System Disorders Somnolence/Sedation 4 6 9 Infections and Infestations Upper Respiratory Tract Infection/Nasopharyngitis 2 4 2 Gastroenteritis 0 2 0 Gastrointestinal Disorders Nausea 1 2 2 Vascular Disorders Hypertension 0 3 < 1 * Includes reactions that occurred at a rate of ≥2% in any doxepin-treated group and at a higher rate than placebo. The most common treatment-emergent adverse reaction in the placebo and each of the doxepin dose groups was somnolence/sedation. 6.2 Studies Pertinent to Safety Concerns for Sleep-promoting Drugs Residual Pharmacological Effect in Insomnia Trials Five randomized, placebo-controlled studies in adults and the elderly assessed next-day psychomotor function within 1 hour of awakening utilizing the digit-symbol substitution test (DSST), symbol copying test (SCT), and visual analog scale (VAS) for sleepiness, following night time administration of doxepin. In a one-night, double-blind study conducted in 565 healthy adult subjects experiencing transient insomnia, doxepin 6 mg showed modest negative changes in SCT and VAS. In a 35-day, double-blind, placebo-controlled, parallel group...

Drug Interactions

7 DRUG INTERACTIONS MAO inhibitors: Doxepin should not be administered in patients on MAOIs within the past two weeks. ( 4.2 ) Cimetidine: Increases exposure to doxepin. ( 7.2 ) Alcohol: Sedative effects may be increased with doxepin. ( 7.3 , 5.4 ) CNS Depressants and Sedating Antihistamines: Sedative effects may be increased with doxepin ( 7.4 , 5.4 ) Tolazamide: A case of severe hypoglycemia has been reported. ( 7.5 ) 7.1 Cytochrome P450 Isozymes Doxepin is primarily metabolized by hepatic cytochrome P450 isozymes CYP2C19 and CYP2D6, and to a lesser extent, by CYP1A2 and CYP2C9. Inhibitors of these isozymes may increase the exposure of doxepin. Doxepin is not an inhibitor of any CYP isozymes at therapeutically relevant concentrations. The ability of doxepin to induce CYP isozymes is not known. 7.2 Cimetidine Doxepin exposure is doubled with concomitant administration of cimetidine, a nonspecific inhibitor of CYP isozymes. A maximum dose of 3 mg is recommended in adults and elderly when cimetidine is co-administered with doxepin [see Clinical Pharmacology (12.3 )] 7.3 Alcohol When taken with doxepin, the sedative effects of alcohol may be potentiated [ see Warnings and Precautions (5.2 , 5.4 )]. 7.4 CNS Depressants and Sedating Antihistamines When taken with doxepin, the sedative effects of sedating antihistamines and CNS depressants may be potentiated [ see Warnings and Precautions (5.2 , 5.4 ) ]. 7.5 Tolazamide A case of severe hypoglycemia has been reported in a type II diabetic patient maintained on tolazamide (1 g/day) 11 days after the addition of oral doxepin (75 mg/day).

Contraindications

4 CONTRAINDICATIONS Hypersensitivity to doxepin hydrochloride, inactive ingredients, or other dibenzoxepines. ( 4.1 ) Co-administration with Monoamine Oxidase Inhibitors (MAOIs): Do not administer if patient is taking MAOIs or has used MAOIs within the past two weeks. ( 4.2 ) Untreated narrow angle glaucoma or severe urinary retention. ( 4.3 ) 4.1 Hypersensitivity Doxepin is contraindicated in individuals who have shown hypersensitivity to doxepin HCl, any of its inactive ingredients, or other dibenzoxepines. 4.2 Co-administration with Monoamine Oxidase Inhibitors (MAOIs) Serious side effects and even death have been reported following the concomitant use of certain drugs with MAO inhibitors. Do not administer doxepin if patient is currently on MAOIs or has used MAOIs within the past two weeks. The exact length of time may vary depending on the particular MAOI dosage and duration of treatment. 4.3 Glaucoma and Urinary Retention Doxepin is contraindicated in individuals with untreated narrow angle glaucoma or severe urinary retention.

Pregnancy and Breastfeeding

8.1 Pregnancy Risk Summary Available data from published epidemiologic studies and postmarketing reports have not established an increased risk of major birth defects or miscarriage (see Data). There are risks of poor neonatal adaptation with exposure to tricyclic antidepressants (TCAs), including doxepin, during pregnancy (see Clinical Considerations). In animal reproduction studies, oral administration of doxepin to rats and rabbits during the period of organogenesis caused adverse developmental effects at doses 65 and 23 times the maximum recommended human dose (MRHD) of 6 mg/day based on AUC, respectively. Oral administration of doxepin to pregnant rats during pregnancy and lactation resulted in decreased pup survival and a delay in pup growth at doses 60 times the MRHD based on AUC (see Data). The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of major birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Clinical Considerations Fetal/Neonatal adverse reactions Neonates exposed to TCAs, including doxepin, late in the third trimester have developed complications requiring prolonged hospitalization, respiratory support, and tube feeding. Such complications can arise immediately upon delivery. Reported clinical findings have included respiratory distress, cyanosis, apnea, seizures, temperature instability, feeding difficulty, vomiting, hypoglycemia, hypotonia, hyperreflexia, tremor, jitteriness, irritability and constant crying. These findings are consistent with either direct toxic effects of TCAs or possibly a drug discontinuation syndrome. Monitor neonates who were exposed to doxepin in the third trimester of pregnancy for poor neonatal adaptation syndrome. Data Human Data Published epidemiologic...

8.3 Females and Males of Reproductive Potential Infertility Based on results from animal fertility studies conducted in rats, doxepin may reduce fertility in females and males of reproductive potential [see Nonclinical Toxicology (13.1 )] . It is unknown if the effects are reversible.

Overdosage

10 OVERDOSAGE Doxepin is routinely administered for indications other than insomnia at doses 10- to 50-fold higher than the highest recommended dose of doxepin. The signs and symptoms associated with doxepin use at doses several-fold higher than the maximum recommended dose (Excessive dose) of doxepin for the treatment of insomnia are described [ see Overdosage (10.1) ], as are signs and symptoms associated with higher multiples of the maximum recommended dose (Critical overdose) [ see Overdosage (10.2) ]. 10.1 Signs and Symptoms of Excessive Doses The following adverse effects have been associated with use of doxepin at doses higher than 6 mg. Anticholinergic Effects : constipation and urinary retention. Central Nervous System : disorientation, hallucinations, numbness, paresthesias, extrapyramidal symptoms, seizures, tardive dyskinesia. Cardiovascular : hypotension. Gastrointestinal : aphthous stomatitis, indigestion. Endocrine : raised libido, testicular swelling, gynecomastia in males, enlargement of breasts and galactorrhea in the female, raising or lowering of blood sugar levels, and syndrome of inappropriate antidiuretic hormone secretion. Other : tinnitus, weight gain, sweating, flushing, jaundice, alopecia, exacerbation of asthma, and hyperpyrexia (in association with chlorpromazine). 10.2 Signs and Symptoms of Critical Overdose Manifestations of doxepin critical overdose include: cardiac dysrhythmias, severe hypotension, convulsions, and CNS depression including coma. Electrocardiogram changes, particularly in QRS axis or width, are clinically significant indicators of tricyclic compound toxicity. Other signs of overdose may include, but are not limited to: confusion, disturbed concentration, transient visual hallucinations, dilated pupils, agitation, hyperactive reflexes, stupor, drowsiness, muscle rigidity, vomiting, hypothermia, hyperpyrexia. 10.3 Recommended Management As management of overdose is complex and changing, it is recommended that the...

How Supplied

16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Doxepin 3 mg tablets are oval shaped, white, identified with debossed markings of “134” on one side and “m” on the other side, and are supplied as: NDC 51407-811-30 Bottle of 30 Doxepin 6 mg tablets are oval shaped, light yellow, identified with debossed markings of “135” on one side and “m” on the other side, and are supplied as: NDC 51407-812-30 Bottle of 30 16.2 Storage and Handling Store at 20° to 25°C (68° to 77°F); excursions permitted between 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Protect from light.