Doxycycline

DOXEFIL (Doxycycline BP 100mg)

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DOXEFIL (Doxycycline BP 100mg)

Doxycycline is a semi-synthetic tetracycline antibiotic and has its main mechanism of action on protein synthesis. It is more lipid soluble and passes directly through the lipid layer of the bacterial cell wall. In addition, an energy dependent active transport system pumps the drug through the inner cytoplasmic membrane. Once inside the bacterial cell, doxycycline inhibits protein synthesis by binding specifically to 30s ribosomes. The drug appears to prevent access of aminoacyl tRNA to the receptor site on the mRNA-ribosome complex. This prevents the addition of amino acids to growing peptide chain.

Therapeutic indications

Doxycycline is used in the treatment of pneumonia, other respiratory tract infections, genitourinary tract infections, soft tissue infections, ophthalmic infections, gastrointestinal infections, acne, Plasmodium falciparum malaria and miscellaneous group of infections.

Contraindications

It is contraindicated in patients hypersensitivity to any of the tetracycline antibiotics, children under 12 years of age and patients with systemic lupus erythematosis.

Dosage and directions for use

Capsule: 2 capsules on first day, then 1 capsule a day, after food. Medication should be carried out for at least 24-48 hours after fever and other symptoms have dissapeared.

Initial treatment of acne: one capsule (100mg doxycycline) daily. The dosage must be reduced as soon as possible to the maintenance dosage of 50mg doxycycline.

Side effects

The side effects of doxycycline include nausea, diarrhoea and symptoms resulting from the overgrowth of non-susceptible organisms. Overgrowth of Candida albicans in the mouth causes soreness, redness and thrush, which may extend into the trachea and bronchi; overgrowth of C. albicans in the bowel results in pruritus ani and there may be overgrowth of resistant coliform organisms, such as Pseudomonas spp and Proteus spp, causing diarrhoea. The most serious supra infection is by resistant Staphylococci, causing a fulminating enteritis with dehydration and occasionally death; this complication is rare, except after abdominal surgery, especially gastrectomy.

Occasionally severe and sometimes fatal liver damage has occurred in pregnant women treated with a tetracycline for pyelonephritis, especially when large doses have been given intravenously.

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Tetracyclines are deposited in calcifying areas in bone and in teeth, causing permanent discolouration and malformation, when given in therapeutic doses to young infants or to women during the late stages of pregnancy, tetracycline interferes with the growth of bones and teeth of infants. Milk teeth are affected if given to children 3 months to six years, and permanent teeth if given to children up to 12 years.

An increase in intracranial pressure which may be associated with a bulging fontanelle in infants, has been reported in patients given tetracyclines. Haemolytic anaemia, eosinophylia, thrombocytopenia have been reported. Vitamin deficiency may occur.

Doxycycline has an anti-anabolic action which may cause a rise in blood urea. Allergic reactions to tetracycline and its analogues have been reported on rare occasions; photosensitivity has occurred.

Warning:

Due to the presence of lactose, the product is contraindicated in patients with congenital galactosemia glucose and galactose malabsorption syndrome or deficit in lactose.

Methyl and Propyl hydroxybenzoates contained in this product are known to cause urticaria; generally delayed type reactions, such as contact dermatitis, but rarely immediate reactions with bronchospasm.

Adverse reactions

There have been reports of prolonged prothrombin time in patients taking warfariin and doxycycline. Because the tetracycline have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.

Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving Vibramycin in conjunction with penicillin.

The absorption of doxycycline is impaired by concurrently administered antacids containing aluminium , calcium, magnesium or other drugs containing these cations; oral zinc, iron salts or bismuth preparations.

The serum half-life of doxycycline is shortened when patients are concurrently receiving alcohol, barbiturates, carbamazepine or phenytoin.

A few cases of pregnancy or breakthrough bleeding have been attributed to the concurrent use of tetracyclines with oral contraceptives.

The concurrent use of tetracycline and methoxyflurane has been reported to result in fatal renal toxicity.

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