DOXEPIN Chemical Properties

Melting point:

187-189°C

Boiling point:

bp0.03 154-157°; bp0.2 260-270°

Density 

1.0594 (rough estimate)

refractive index 

1.5000 (estimate)

storage temp. 

Sealed in dry,2-8°C

pka

9.40±0.28(Predicted)

Water Solubility 

31.57mg/L(25 ºC)

EPA Substance Registry System

Doxepin (1668-19-5)

Safety Information

Hazard Codes 

T

Risk Statements 

25

Safety Statements 

36/37/39-45

Hazardous Substances Data

1668-19-5(Hazardous Substances Data)

Toxicity

LD50 in mice, rats (mg/kg): 26, 16 i.v.; 79, 182 i.p.; 135, 147 orally (Ribbentrop, Schaumann)

DOXEPIN Usage And Synthesis

Originator

Sinequan,Pfizer,US,1969

Uses

Used clinically to treat anxiety and depression. Antidepressant

Definition

ChEBI: A dibenzooxepine that is 6,11-dihydrodibenzo[b,e]oxepine substituted by a 3-(dimethylamino)propylidene group at position 11. It is used as an antidepressant drug.

Manufacturing Process

(A) Preparation of 3-bromopropyltriphenylphosphonium bromide: Triphenylphosphine, 1.0 kg, and 770 grams of 1,3-dibromopropane are dissolved in 2.0 liters of xylene and the solution is stirred under a nitrogen atmosphere at 130°C. After 20 hours the mixture is cooled, and the crystalline product, which precipitates, is collected and washed with 20 liters of benzene. After drying in vacuo the product weighs 1,578 grams, MP 229°-230°C;titration for bromide ion: Found, 17.1%; calculated, 17.2%.
(B) Preparation of 3-dimethylaminopropyltriphenylphosphonium bromide hydrobromide: A solution of 595 grams of anhydrous dimethylamine and 1,358 grams of 3-bromopropyl-triphenylphosphonium bromide in 4 liters of ethanol is warmed to 70°C until solution is complete and the solution then is allowed to stand at room temperature for 20 hours. Volatile components are removed by distillation in a vacuum and the residue is suspended in 2.0 liters of ethanol and is redistilled to remove excess amine. The residue is dissolved in 3.0 liters of warm ethanol and gaseous hydrogen bromide is passed into the solution until the mixture is acidic. After filtration the solution is concentrated to a volume of 3.0 liters, is cooled, whereupon the product precipitates, and the precipitate is collected; it weighs 1,265 grams, MP 274- 281°C. Recrystallization from ethanol raises the MP to 280.5°-282.5°C. Bromide ion titration: Found, 31.2%; calculated 31.3%.
(C) Preparation of doxepin: 1,530 grams of the product from step (B) is suspended in 4.5 liters dry tetrahydrofuran and 6.0 mols of butyl lithium in heptane is added during 1 hour. After an additional 30 minutes, 483 grams of 6,11-dihydrodibenz-(b,e)oxepin-11-one, prepared as described in Belgian Patent 641,498, is added to the deep red solution and the reaction was maintained at reflux for 10 hours. Water, 500 ml, is added at room temperature and the solvent is removed in vacuo. The crude residue is treated with 10% hydrochloric acid until acidic (pH 2) and then 1.5 liters benzene is added. After stirring, the mixture separates into 3 phases (an insoluble hydrochloride salt product phase, an aqueous phase and an organic phase).
The benzene layer is removed by decantation and the remaining mixture is rendered basic with 10% sodium hydroxide solution and is extracted with three 1,500 ml portions of benzene. The benzene extracts are washed, then dried with anhydrous sodium sulfate and concentrated in a vacuum leaving a residue of 1,530 grams, gas and thin layer chromatography analysis show this to be a cis/trans mixture (approx. 4:l) of 11-dimethylaminopropylidene-6,11- dihydrodibenz-(b,e)oxepin (90% yield). This mixture has substantially more activity pharmacologically than the cis/trans mixture obtained by the Grignard route disclosed in the Belgian Patent 641,498. This base is then converted to the hydrochloride with HCl.

brand name

Apo-doxepin;Co dox;Deptran;Doksapan;Dolat;Doxal;Doxedyn;Doxepin hcl;Gilex;Novo-doxepin;Novoxapin;Sinequan;Sinquan concentrate;Sinquane;Tolllluan;Triadapin;Zonalon.

Therapeutic Function

Tranquilizer

World Health Organization (WHO)

Doxepin, a tricyclic antidepressant was introduced in 1964 for the management of endogenous depression. Much of the adverse effects are caused by its antimuscarinic actions. These include dry mouth, cardiac arrhythmias, central nervous system disturbances, blood disorders and risk of suicide. The risk of suicide and dangers related to overdosage led the Norwegian Medicines Control Authority to put the higher strength formulation under prescribing restriction in 1992. The risk of death following overdosage is apparently higher for products containing tricyclic compounds as compared with nontricyclic products.

Biological Activity

Highly potent H 1 histamine receptor antagonist (K d = 310 pM) and tricyclic antidepressant. Also binds to the H 4 histamine receptor (pK i = 6.79).

Contact allergens

This benzoxepin tricylcic drug has antidepressant, anticholinergic, antiitching, and antihistamine properties. After oral use, it has been developed as a topical antiitching agent. Allergic contact dermatitis is not infrequent.

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