Oxydihy 20%

Indications

• Bacterial infections (e.g. Chlamydia, Rickettsia, Mycoplasma)
• Acne
• Prophylaxis of asymptomatic meningococcal carrier state (not recommended)

Dosage

Adults: For adult patients, the typical dosage of oxytetracycline for susceptible infections is 100 mg twice daily for 5 days. For other conditions, such as acne, the dosage may be 500 mg twice daily, usually for a duration of 6 to 12 weeks, with the possibility of repeating the course intermittently.

Mechanism of action

Oxytetracycline exerts its antibacterial effects by binding to the 30S ribosomal subunit of bacteria, inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex. This action prevents the synthesis of proteins essential for bacterial growth and replication, leading to the bacteriostatic effect of the drug.

Pharmacodynamics

The pharmacodynamics of oxytetracycline involve its ability to inhibit bacterial protein synthesis, which is critical for the growth and reproduction of bacteria. The drug demonstrates a broad spectrum of activity against both Gram-positive and Gram-negative organisms, as well as some atypical pathogens. Its effectiveness can be influenced by the presence of tetracycline resistance mechanisms in certain bacterial strains.

Pharmacokinetics

Oxytetracycline is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 1-2 hours after oral administration. It has a relatively long half-life of about 8-10 hours, allowing for twice-daily dosing. The drug is widely distributed in body tissues and fluids, including the liver, kidneys, and lungs, but is less effective in central nervous system infections due to limited penetration. It is primarily excreted via urine, and dosage adjustments may be necessary in patients with renal impairment.

Contra-indications

• Children under 12 years due to deposition in growing bone and teeth, causing staining and occasionally dental hypoplasia

Adverse effects

• Gastrointestinal disturbances
• Photosensitivity
• Dental discoloration
• Hepatotoxicity
• Renal impairment
• Skin reactions including rash and urticaria
• Ataxia
• Hearing impairment
• Colitis
• Systemic lupus erythematosus exacerbation

Interactions

• Antacids and supplements containing calcium, magnesium, or iron may reduce absorption
• Oral contraceptives may be less effective
• Other tetracyclines
• Warfarin (may increase anticoagulant effect)

Precautions

• Use with caution in patients with renal impairment
• Monitor for hepatic toxicity in long-term use
• Patients should be advised to avoid excessive sunlight exposure
• Discontinue if systemic lupus erythematosus develops or worsens

Pregnancy

Oxytetracycline is contraindicated during pregnancy due to potential harm to fetal development, particularly affecting bone and dental health.

Breast-feeding

Use with caution; oxytetracycline is excreted in breast milk and may affect the infant's dental health.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Oxytetracycline 250 mg tablets
• Oxytetracycline oral suspension
• Oxytetracycline oral solution