Doxycycline

Doxycycline: Uses, Dosage and Side Effects

Overview

• An antimicrobial agent that inhibits protein synthesis at the initiation step by interacting with the 30S subunit of the ribosome.

Uses of Doxycycline

• Antibacterial (including spirochaetes like Helicobacter and Campylobacter), anti-rickettsial, anti-mycoplasmal (for instance, Mycoplasma haemofelis), and antichlamydial activity.
• It is the treatment of choice for feline chlamydiosis; cats may require 3–4 weeks of treatment.
• It is also an adjunctive treatment for canine heartworm disease because it eliminates the symbiont Wolbachia.

Dose of Doxycycline in Dogs and Cats

Dogs, Cats:

10 mg/kg p.o. q24h with food

Side Effects of Doxycycline in Dogs and Cats

• Vomiting and diarrhoea.
• To avoid oesophagitis and ulceration, give with food or water.
• During tooth development, it may discolour teeth, but less than other tetracyclines.
• Doxycycline monohydrate is less acidic than doxycycline hyclate, the UK-approved salt.
• Doxycycline monohydrate reduces human oesophageal ulcers.

Contraindications of Doxycycline in Dogs and Cats

• Do not administer to pregnant animals.
• Do not administer if there is evidence of oesophagitis or dysphagia.

Some Notes:

• It is not affected by, and does not affect, renal function as it is excreted in faeces, and is therefore recommended when tetracyclines are indicated in animals with renal impairment.
• Being extremely lipid-soluble, it penetrates well into prostatic fluid and bronchial secretions.
• Administer with food.
• Absorption of doxycycline is reduced by antacids, calcium, magnesium and iron salts, although the effect is less marked than seen with water-soluble tetracyclines.
• Phenobarbital and phenytoin may increase its metabolism, thus decreasing plasma levels.