What is the maximum dosage of Isoniazid (INH) for anti-tubercular treatment?

From the Guidelines

The maximum dosage of isoniazid for tuberculosis treatment is 300 mg per day for adults, regardless of weight, as recommended by the most recent guidelines 1.

Key Considerations

• For children, the maximum dose is 5 mg/kg every 24 hours, with a maximum daily dose of 300 mg, as per the European Association of Urology guidelines 1.
• In certain situations, such as twice or thrice weekly directly observed therapy (DOT), the maximum dose may be increased, but the standard maximum dose is 300 mg per day for adults.
• Isoniazid is a key component of standard tuberculosis treatment regimens, typically used alongside other medications like rifampin, ethambutol, and pyrazinamide in the intensive phase.
• Pyridoxine (vitamin B6) supplementation is recommended with isoniazid therapy to prevent peripheral neuropathy, especially in malnourished patients, pregnant women, or those with conditions like diabetes, HIV, or alcoholism.

Dosage and Administration

• The dosage of isoniazid is 5 mg/kg every 24 hours, with a maximum daily dose of 300 mg, as per the European Association of Urology guidelines 1.
• The treatment regimen for newly diagnosed genitourinary tuberculosis (GUTB) includes isoniazid, rifampicin, pyrazinamide, and ethambutol in the intensive phase, followed by isoniazid and rifampicin in the continuation phase 1.

Special Considerations

• Dose adjustments may be necessary for patients with severe renal impairment or hepatic dysfunction, and liver function should be monitored regularly during treatment due to potential hepatotoxicity.
• The guidelines recommend individualized treatment regimens for multidrug-resistant tuberculosis (MDR-TB), including at least 5 effective TB medicines during the intensive phase, including pyrazinamide and 4 core second-line TB medicines 1.

From the FDA Drug Label

Adults: 5 mg/kg up to 300 mg daily in a single dose; or 15 mg/kg up to 900 mg/day, two or three times/week Children: 10 - 15 mg/kg up to 300 mg daily in a single dose; or 20-40 mg/kg up to 900 mg/day, two or three times/week The maximum dosage of isoniazid for anti-tubercular treatment is 900 mg/day for adults and 900 mg/day for children, as indicated in the dosage guidelines 2.

• The dosage is weight-based, with a maximum of 15 mg/kg for adults and 20-40 mg/kg for children.
• The dosage frequency can be daily or two to three times a week, depending on the treatment regimen.

From the Research

Maximum Dosage of Isoniazid

The maximum dosage of isoniazid is not explicitly stated in the provided studies. However, the following information can be gathered:

• The study 3 mentions that children were administered 1,2,3, or 4 FDC tablets (rifampicin/isoniazid/pyrazinamide 75/50/150 mg) daily for 4-8-12-16, and 16-25 kg weight bands, respectively.
• The study 4 does not provide information on the maximum dosage of isoniazid.
• The study 5 suggests that high-dose treatment with isoniazid may be necessary to reduce the incidence of isoniazid mono-resistant and multi-drug resistant (MDR) tuberculosis.
• The study 6 mentions that patients with isoniazid-resistant tuberculosis were treated with a regimen of isoniazid, rifampin, pyrazinamide, and ethambutol daily for 6 months, but does not specify the maximum dosage of isoniazid.
• The study 7 mentions that most studies used isoniazid for 9 months, but does not provide information on the maximum dosage.

Key Points

• The maximum dosage of isoniazid is not explicitly stated in the provided studies.
• High-dose treatment with isoniazid may be necessary to reduce the incidence of isoniazid mono-resistant and multi-drug resistant (MDR) tuberculosis 5.
• Isoniazid is commonly used for 9 months in the treatment of latent tuberculosis infection 7.
• The dosage of isoniazid may vary depending on the patient's weight and other factors 3.

Dosage Considerations

• The study 3 suggests that the dosage of isoniazid may need to be adjusted based on the patient's weight.
• The study 4 mentions that the dose per kilogram of body weight was associated with the concentrations of all four agents (rifampin, isoniazid, pyrazinamide, and ethambutol).
• The study 5 suggests that personalized diagnostics and targeted high-dose treatment with isoniazid may be necessary to reduce the incidence of isoniazid mono-resistant and multi-drug resistant (MDR) tuberculosis.