Rifampicin and Isoniazid

Rifampicin and isoniazid are two antibiotics commonly used together to treat tuberculosis (TB). Rifampicin is a broad-spectrum antibiotic known for its ability to inhibit RNA synthesis in bacteria, while isoniazid specifically targets the cell wall synthesis of TB-causing bacteria. When combined, these medications are highly effective in eradicating the TB bacteria and preventing resistance.

Indications

The combination of rifampicin and isoniazid is primarily indicated for the treatment of active tuberculosis, particularly pulmonary TB. It is also used for TB prophylaxis in high-risk individuals and for latent TB infection to prevent progression to active disease.

Dosage

Dosage of rifampicin and isoniazid can vary based on the patient's weight, age, and severity of infection. Typically, adult dosages are around 600 mg per day for rifampicin and 300 mg per day for isoniazid, taken together as part of a combination therapy regimen. Pediatric dosages vary based on weight and should be prescribed by a healthcare professional. Treatment duration generally lasts for 6-12 months, depending on the severity and response to therapy.

Contra-Indications

Both rifampicin and isoniazid should be avoided in patients with known hypersensitivity to these drugs. They are contraindicated in patients with severe hepatic impairment, as both drugs can cause liver toxicity. Isoniazid should not be used in patients with acute liver disease. Caution should be taken in patients with a history of alcohol use disorder or previous liver issues.

Special Precautions

Patients taking rifampicin and isoniazid should undergo regular liver function tests due to the risk of hepatotoxicity. Monitoring for peripheral neuropathy is also important, especially with isoniazid, as it can be prevented by pyridoxine (vitamin B6) supplementation. Additionally, rifampicin may cause bodily fluids (such as urine and tears) to turn reddish-orange, which is a harmless side effect but can stain contact lenses and clothing.

Side Effects

Common side effects include gastrointestinal disturbances, such as nausea and vomiting, as well as skin rash. More serious but rare side effects include liver toxicity, hepatitis, and peripheral neuropathy. Patients may also experience flu-like symptoms, fatigue, and dizziness. Rifampicin may discolor bodily fluids, including urine, sweat, and tears.

Drug Interactions

Rifampicin is a potent inducer of cytochrome P450 enzymes, which can decrease the effectiveness of other medications such as oral contraceptives, anticoagulants, and some antiviral drugs. Isoniazid may inhibit the metabolism of certain drugs, such as phenytoin, leading to elevated levels. Always consult a healthcare provider for potential interactions.