Doxepin

log Kow = 0.67

4

3.75

WHITE CRYSTALLINE SUBSTANCE; 1 G SOL IN 1 ML WATER, 2 ML ALCOHOL, 10 ML CHLOROFORM /HYDROCHLORIDE/

In water, 31.57 mg/l at 25 °C.

3.19e-02 g/L

154-157 ºC at 0.03 mmHg

154-157 °C @ 0.03 MM HG

185-191 ºC

Crystals, melting point 184 to 186 °C, 188 to 189 °C (a cis-trans mixture of approx 1:5) /HYDROCHLORIDE/

Crystals, melting point 161 to 164 °C, 168 to 169 °C /MALEATE/

Melting point 192 to 193 °C /trans-HYDROCHLORIDE/

Crystals, melting point 209 to 210.5 °C /cis-HYDROCHLORIDE/

184 - 186 °C

Manufacturers, packers, and distributors of drug and drug products for human use are responsible for complying with the labeling, certification, and usage requirements as prescribed by the Federal Food, Drug, and Cosmetic Act, as amended (secs 201-902, 52 Stat. 1040 et seq., as amended; 21 U.S.C. 321-392).

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Obtain an ECG and immediately initiate cardiac monitoring. Protect the patient's airway, establish an intravenous line and initiate gastric decontamination. A minimum of six hours of observation with cardiac monitoring and observation for signs of CNS or respiratory depression, hypotension, cardiac dysrhythmias and/or conduction blocks, and seizures is strongly advised. If signs of toxicity occur at any time during this period, extended monitoring is recommended. (L1712)

/DOXEPIN/...MAY...POTENTIATE THE DEPRESSANT EFFECT OF ALCOHOL. /HYDROCHLORIDE/

INHIBITION OF THE ANTIHYPERTENSIVE EFFECT OF GUANETHIDINE CAN OCCUR WITH DOSES OF 200-300 MG/DAY. /HYDROCHLORIDE/

DOXEPIN MAY POTENTIATE ORAL ANTICOAGULANTS, AMPHETAMINES, OTHER ANTICHOLINERGICS, MEPROBAMATE, PHENOTHIAZINES, THIOXANTHENE TRANQUILIZERS. DOXEPIN MAY ANTAGONIZE PROPRANOLOL /THEORETICALLY/, METHYLDOPA. DOXEPIN MAY BE ANTAGONIZED BY BARBITURATES. DOXEPIN MAY BE POTENTIATED BY THYROID PREPN.

DOXEPIN MAY FORM HAZARDOUS COMBINATIONS WITH RESERPINE, ESTROGENS, PSYCHOTROPICS, MAO INHIBITORS, BENZODIAZEPINES.

For more Interactions (Complete) data for DOXEPIN (28 total), please visit the HSDB record page.

hypotension, postural collapse (if patient arises too fast from lying/sitting position to standing), arrhythmias (sinus-tachycardia, bradycardia, av-blockade). Allergic/toxic effetcs also include skin rash, photosensitivity, liver damage of the cholostatic type (rarely), hepatitis (extremely rare), leuko- or thrombopenia (rarely), agranulocytosis (very rarely), hypoplastic anemia (rarely). [Wikipedia]

Liver test abnormalities have been reported to occur in up to 16% of patients being treated with tricyclic antidepressants, but elevations are uncommonly above 3 times the upper limit of normal. The aminotransferase abnormalities are usually mild, asymptomatic and transient, reversing even with continuation of medication. Rare instances of clinically apparent acute liver injury have been reported due to doxepin, but the number of cases have been too few to characterize the clinical features. Recurrent jaundice and marked aminotransferase elevations with repeated exposures to doxepin has been reported. Most cases have been mild and deaths from acute liver failure or chronic injury have not been reported.

Doxepin is a unique antidepressant because it produces different adverse effects based on the receptor it antagonizes. Doxepin antagonizes 3 different receptors: histamine, adrenergic, and muscarinic. Doxepin blocks histamine H1 receptor and causes sedation and somnolence; therefore, FDA has approved low-dose doxepin, 3 mg, and 6 mg dosages as a first-line agent in depressed patients with sleep disturbances and depression associated with anxiety. Proper education is necessary to prevent patients from self-medicating and overdosing with these doses.

TCAs are one of the most frequently ingested substances used for self-poison in an attempt to commit suicide. A case fatality index is a tool used to measure ratios and compare toxic levels of drugs to one another. Tricyclics have a greater incidence of toxicity than other antidepressants, and doxepin is 2 to 3 times more toxic when compared to amitriptyline.

The mechanism of action of doxepin is not completely understood. It is thought that like amitriptyline, doxepin enhances the actions of norepinephrine and serotonin by blocking their reuptake at the neuronal membrane. However, doxepin weakly inhibits the reuptake of dopamine. Doxepin may also act on histamine H₁-receptors, resulting in sedative effects, and β-adrenergic receptors. It is also an antagonist of 5-hydroxytryptamine (serotonin) receptors, alpha-1 adrenergic receptor, and muscarinic cholinergic receptors.

ALTHOUGH MOST FATAL CASES OF DOXEPIN POISONING HAVE RESULTED FROM INGESTION OF MORE THAN 1.5 G, DEATH HAS BEEN REPORTED AFTER INGESTION OF 850 MG & RECOVERY AFTER...5 G. /HYDROCHLORIDE/

DOXEPIN OVERDOSE PATIENTS SHOWED QRS DURATION OF 100 MSEC OR MORE ON ROUTINE ECG WITHIN 1ST 24 HR.

A 36-year-old woman was treated with doxepin, 10 mg daily, for approximately 5 weeks starting 2 weeks after the birth of her daughter. The dose was increased to 25 mg three times daily 4 days before the wholly breast-fed 8-week-old infant was found pale, limp, and near respiratory arrest. Although drowsiness and shallow respirations continued on admission to the hospital, the baby made a rapid recovery and was normal in 24 hours.

Drug-Induced Liver Injury Severity and Toxicity (DILIst)

doxepin

DILI Positive

Oral

DOI:10.1016/j.drudis.2019.09.022

Manufacturers, packers, and distributors of drug and drug products for human use are responsible for complying with the labeling, certification, and usage requirements as prescribed by the Federal Food, Drug, and Cosmetic Act, as amended (secs 201-902, 52 Stat. 1040 et seq., as amended; 21 U.S.C. 321-392).

N - Nervous system

D - Dermatologicals

QN - Nervous system

QD - Dermatologicals

Similar to other tricyclic antidepressants, doxepin was shown, in preclinical trials, to decrease the electrical activity of the brain, prolong the hexobarbital-induced sleep and block avoidance behavior without affecting the conditioned emotional response. At high doses, it also produces symptoms of central nervous system depression. Doxepin is known to cause antidepressant, sedative, and anticholinergic effects. At high doses, its anticholinergic and antiadrenergic properties are the most prevalent which limit its efficacy. These effects are observed at high doses where its affinity for H1 histamine receptor is lost and its binding to other receptors is observed. The maximal antidepressive effects of doxepin are present around two weeks following initiation of therapy. However, the sedative effects of doxepin, usually used for the treatment of insomnia or anxiety, are observed immediately after administration.

Doxepin exact mechanism of action is not very clear. However, doxepin is known to be a selective histamine H1 receptor blocker. This effect on histamine receptors indicates effectiveness in skin conditions. Breaking its function according to the different effect, doxepin's antidepressive action is primarily associated with the inhibition of the central nervous system biogenic amine reuptake; more specifically, norepinephrine and serotonin at synaptic nerve terminals. This effect increases the level of monoamines in the synaptic site which in order increases the activity at the post-synaptic neuron receptor sites. It has been suggested that doxepin also desensitizes both serotonin 1A receptors and beta-adrenergic receptors. It is known that the lack of dopamine transporters in the frontal cortex and the transmission of dopamine in this region is largely inactivated by the effect of norepinephrine reuptake. Hence, doxepin action on the frontal cortex is suggested to increase dopamine neurotransmission in this area.

ACTION OF TRICYCLIC ANTIDEPRESSANTS ON CATECHOLAMINES & INDOLEAMINES IN BRAIN...BLOCK RE-UPTAKE OF NOREPINEPHRINE BY ADRENERGIC NERVE TERMINALS. /TRICYCLIC ANTIDEPRESSANTS/

The mean elimination half-life is reported to be of 15 hours.

AFTER ORAL 75 MG DOXEPIN-HCL TO HUMANS, PEAK PLASMA CONCN 8.8-45.8 NG/ML, REACHED WITHIN 4 HR. DISAPPEARANCE OF DOXEPIN WAS BIPHASIC & FOLLOWED 1ST-ORDER KINETICS. MEAN DOXEPIN T/2 WAS 16.8 HR. MEAN APPARENT VOL OF DISTRIBUTION WAS 20.2 L/KG.

Doxepin is extensively metabolized to N-desmethyldoxepin which is a biologically active metabolite and other inactive metabolites. The first-pass metabolism accounts for 55-87% of the administered dose. After, the secondary metabolism is driven by the transformation of N-desmethyldoxepin to its glucuronide conjugates. The main metabolic enzymes involved in the transformation of doxepin are the members of the cytochrome P450 family, CYP2C19 and CYP2D6 with minor involvement of CYP1A2 and CYP2C9.

AFTER ORAL DOSING OF DOXEPIN-HCL TO HUMANS, METABOLITE DESMETHYLDOXEPIN WAS PRODUCED.

Extensively metabolized in the liver via the same pathways as other TCAs. <i>N</i>-demethylation produces an active metabolite, <i>N</i>-desmethyldoxepin. CYP2D6 specifically hydroxylates the E-isomer. Half Life: 6 - 24.5 hours

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DOXEPIN

Established Pharmacologic Class [EPC] - Tricyclic Antidepressant

Doxepin is a Tricyclic Antidepressant.

DOXEPIN

Tricyclic Antidepressant [EPC]

Substances that contain a fused three-ring moiety and are used in the treatment of depression. These drugs block the uptake of norepinephrine and serotonin into axon terminals and may block some subtypes of serotonin, adrenergic, and histamine receptors. However, the mechanism of their antidepressant effects is not clear because the therapeutic effects usually take weeks to develop and may reflect compensatory changes in the central nervous system.

Drugs used to induce SLEEP, prevent SLEEPLESSNESS, or treat SLEEP INITIATION AND MAINTENANCE DISORDERS.

Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonists. Classical antihistaminics block the histamine H1 receptors only.

Doxepin is moderately absorbed following oral ingestion with a bioavailability of 30%. The median peak concentration of doxepin ranges from 8.8-45.8 ng/ml and it is achieved 3.5 hours after initial administration. Its absorption is increased with concomitant administration of a high-fat meal.

The elimination profile of doxepin is presented as biphasic. It is excreted in the urine mainly in the form of glucuronide conjugates. Less than 3% of a doxepin dose is excreted in the urine as parent compound or nordoxepin.

The mean apparent volume of distribution of doxepin is reported to be of 20 L/kg.

The mean total apparent plasma clearance of a single oral dose of 50 mg doxepin in healthy individuals is 0.93 l/hr/kg.

/DOXEPIN HAS/...A PECULIAR AFFINITY FOR UVEAL MELANIN...ALSO...BOUND BY OCULAR MELANIN BOTH IN VIVO & IN VITRO.

AFTER HUMAN ORAL DOSE 75 MG DOXEPIN-HCL, EST 1ST-PASS METAB RANGED FROM 55-87% OF ORAL DOSE ASSUMING COMPLETE ABSORPTION.

THERAP CAT: Antidepressant; THERAP CAT (VET): Antipruritic.

MEDICATION

Use (kg; approx.) in Germany (2009): >5000

Doxepin is used for the treatment of depression, insomina, alcohol and drug withdrawal, gastrointestinal ulceration and other GI-problems. It can also be used for chronic urticaria and in the management of pain.

Prepn of mixture of cis- trans-isomers: K. Stach, F. Bickelhaupt, Monatsh 93, 896 (1962); F. Bickelhaupt et al. Monatsh 95, 485 (1964); Neth pat Appl 6,407,758; K Stach, U.S. pat 3,438,981 (1965, 1969 both to Boehringer Mann); and separation and activity of isomers: B.M. Bloom, J.R. Tretter, Belg pat 641,498; eidem, U.S. pat 3,420,851 (1964, 1969 both to Pfizer).

6,11-DIHYDRODIBENZ[B,E]OXEPIN-11-ONE...PREPARED FROM PHTHALIDE & CONVERTED TO 11-[3-(DIMETHYLAMINO)PROPYL]-6H-DIBENZ[B,E]OXEPIN-11-OL THRU GRIGNARD REACTION WITH 3-(DIMETHYLAMINO)PROPYL CHLORIDE. DEHYDRATION OF THE ALCOHOL WITH MINERAL ACID YIELDS DOXEPIN WHICH IS REACTED WITH HCL. /HYDROCHLORIDE/

Methyl salicylate + benzyl chloride + 3-dimethylaminopropyl chloride hydrochloride (ether formation/cyclization/Grignard reagent formation/Grignard reaction/dehydration).