Name:  Doxycycline hydrochloride

Synonyms:  (4S,4aR,5S,5aR,6R,12aS)-4-(Dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,5,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide hydrochloride

Molecular Structure:  

Molecular Formula:  C₂₂H₂₄N₂O₈.HCl

Molecular Weight:  480.90

CAS Number:  10592-13-9

EINECS:  234-198-7

 

Doxycycline hydrochloride is a yellow hygroscopic crystalline powder. Doxycycline hydrochloride 115 mg is approximately equivalent to 100 mg of doxycycline. Ph. Eur. solubilities are: freely soluble in water and in methyl alcohol; sparingly soluble in alcohol; practically insoluble in ether; dissolves in solutions of alkali hydroxides and carbonates. USP solubilities are: soluble in water; slightly soluble in alcohol; practically insoluble in chloroform and in ether; soluble in solutions of alkali hydroxides and carbonates. A 1% solution in water has a pH of 2 to 3. Store in air tight containers. Protect from light.

Preparations of doxycycline hydrochloride have an acid pH and incompatibility may reasonably be expected with alkaline preparations or with drugs unstable at low pH. Reduced antimicrobial activity has been reported in vitro when doxycycline hydrochloride was mixed with riboflavine.

Doxycycline is a tetracycline derivative with uses similar to those of tetracycline. Doxycycline may sometimes be preferred to other tetracycline's in the treatment of sensitive infections because of its fairly reliable absorption and its long half-life which permits less frequent (often once daily) dosage. Doxycycline also has the advantage that it can be given (with care) to patients with renal insufficiency. However, relatively high doses may need to be given for urinary-tract infections because of its low renal excretion.

Doxycycline is normally administered by mouth as doxycycline or its various derivatives. Doses are expressed in terms of doxycycline. The usual dose is 200 mg of doxycycline on the first day, followed by 100 mg daily. Doxycycline is used in some areas for the treatment of chloroquine-resistant falciparum malaria in a dose of 200 mg daily for at least 7 days in combination with quinine. Doxycycline 100 mg daily has been used for prophylaxis in areas of high risk where other drugs are likely to be ineffective, but Doxycycline is not suitable for extended prophylactic use.