Isoniazid / Rifampin Dosage

Applies to the following strengths: 150 mg-300 mg

Usual Adult Dose for Tuberculosis - Active

2 capsules (300 mg isoniazid and 600 mg rifampin total dose) orally once a day on an empty stomach, either 1 hour before or 2 hours after ingestion of food or antacids.

Duration of Therapy: At least 4 months following the initial treatment phase; continue treatment longer if the patient is still sputum or culture positive, if resistant organisms are present, or if the patient is HIV-positive.

Use: Treatment for pulmonary tuberculosis in which organisms are susceptible, and when the patient has been titrated on the individual components of this combination drug and thus, it has been established that the fixed dosage of this combination drug is therapeutically effective.

Usual Geriatric Dose for Tuberculosis - Active

Use with caution.

Usual Pediatric Dose for Tuberculosis - Active

Younger Than Age 15 Years: The ratio of isoniazid and rifampin in this combination drug may not be appropriate (e.g., pediatric patients usually receive higher mg/kg doses of isoniazid)

Age 15 Years and Older:
2 capsules (300 mg isoniazid and 600 mg rifampin total dose) orally once a day on an empty stomach, either 1 hour before or 2 hours after ingestion of food or antacids, following the initial treatment phase.

Duration of Therapy: At least 4 months following the initial treatment phase; continue treatment longer if the patient is still sputum or culture positive, if resistant organisms are present, or if the patient is HIV-positive.

Use: Treatment for pulmonary tuberculosis in which organisms are susceptible, and when the patient has been titrated on the individual components of this combination drug and thus, it has been established that the fixed dosage of this combination drug is therapeutically effective.

Renal Dose Adjustments

No adjustment recommended; however, carefully monitor use in patients with severe renal dysfunction.

Liver Dose Adjustments

Severe Hepatic Damage; Acute Liver Disease of Any Etiology: Contraindicated.
Impaired Liver Function: Use with caution and under strict medical supervision.

Comments: If this drug is given to patients with impaired liver function, carefully monitor liver function (especially SGPT and SGOT) prior to therapy, then every 2 to 4 weeks during therapy; withdraw treatment if signs of hepatocellular damage occur.

Precautions

US BOXED WARNING:

Severe and sometimes fatal hepatitis associated with isoniazid therapy may occur and may develop even after many months of treatment.
The risk of developing hepatitis is increased with daily consumption of alcohol; and in general, the incidence of hepatitis increases with age.
Serum transaminase concentration becomes elevated in about 10% to 20% of patients, usually during the first few months of therapy but can occur at any time.
Liver enzyme levels often return to normal despite continuance of isoniazid, but cases of progressive liver dysfunction have occurred.
Patients given isoniazid should be carefully monitored and interviewed at monthly intervals; patients should immediately report if they experience any of the prodromal hepatitis symptoms (e.g., fatigue, weakness, malaise, anorexia, nausea, vomiting).
This drug should be promptly discontinued if signs/symptoms of hepatic damage are detected as isoniazid has been reported to cause a more severe form of liver damage.
If this drug is discontinued, patients with tuberculosis should be given appropriate treatment with alternative drugs.
If isoniazid must be reinstated, treatment should be resumed only after symptoms and laboratory abnormalities have cleared.
This drug should be restarted in very small and gradually increasing doses and should be immediately withdrawn if there is any indication of recurrent liver involvement.
Treatment should be deferred in persons with acute hepatic diseases.

Safety and efficacy have not been established in patients younger than 15 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available.

Other Comments

Administration Advice:

Concomitant administration of pyridoxine (Vitamin B6) is recommended in the malnourished, in those predisposed to neuropathy (e.g., alcoholics and diabetics), and in adolescents.

Storage Requirements:

Store at 25 degrees Celsius/77 degrees Fahrenheit; excursions permitted to 15 to 30 degrees C/59 to 86 degrees F.
Protect from moisture and excessive humidity.

General:

This fixed-dosage combination drug (150 mg isoniazid and 300 mg rifampin per capsule) is not recommended for initial therapy of tuberculosis or for preventive therapy.
This drug is not indicated for the treatment of meningococcal infections or asymptomatic carriers of Neisseria meningitis to eliminate meningococci from the nasopharynx.

Monitoring:
DERMATOLOGIC: Skin reactions (e.g., signs/symptoms of progressive skin rash often with blisters or mucosal lesions)
GENERAL:

Baseline measurements of serum creatinine, complete blood count, platelet count, and blood uric acid.
Carefully monitor use of this drug in patients with chronic liver disease, severe renal dysfunction, slow acetylator status, epilepsy, history of psychosis, history of peripheral neuropathy, diabetes, alcohol dependence, HIV infection, or porphyria.
Evaluate patients at least monthly during treatment, and specifically question them about symptoms associated with adverse reactions.
Follow-up with all patients with abnormalities, including laboratory testing if necessary.

HEPATIC: Baseline measurements of liver function (e.g., hepatic enzymes, bilirubin)
OCULAR: Ophthalmologic exams including ophthalmoscopy (before treatment initiation and periodically thereafter)
OTHER: Collect specimens (bacteriologic smears or cultures) for identification of the infecting organism and to confirm the susceptibility of the organism to rifampin and isoniazid prior to treatment initiation; repeat throughout therapy.

Patient Advice:

This drug may cause side effects such as vertigo, vision problems, and psychotic reactions; avoid potentially dangerous activities such as driving and operating machinery until you know how this drug affects you.