Pyrazinamide (Page 2 of 3)

ADVERSE REACTIONS:

General:

Fever, porphyria and dysuria have rarely been reported. Gout (see PRECAUTIONS:).

Gastrointestinal:

The principal adverse effect is a hepatic reaction (see WARNINGS:). Hepatotoxicity appears to be dose related, and may appear at any time during therapy. GI disturbances including nausea, vomiting and anorexia have also been reported.

Hematologic and Lymphatic:

Thrombocytopenia and sideroblastic anemia with erythroid hyperplasia, vacuolation of erythrocytes and increased serum iron concentration have occurred rarely with this drug. Adverse effects on blood clotting mechanisms have also been rarely reported.

Other:

Mild arthralgia and myalgia have been reported frequently. Hypersensitivity reactions including rashes, urticaria, and pruritis have been reported. Fever, acne, photosensitivity, porphyria, dysuria and interstitial nephritis have been reported rarely.

OVERDOSAGE:

Overdosage experience is limited. In one case report of overdose, abnormal liver function tests developed. These spontaneously reverted to normal when the drug was stopped. Clinical monitoring and supportive therapy should be employed. Pyrazinamide is dialyzable. 13

DOSAGE AND ADMINISTRATION:

Pyrazinamide should always be administered with other effective antituberculous drugs. It is administered for the initial 2 months of a 6-month or longer treatment regimen for drug-susceptible patients. Patients who are known or suspected to have drug-resistant disease should be treated with regimens individualized to their situation.

Pyrazinamide frequently will be an important component of such therapy.

Patients with concomitant HIV infection may require longer courses of therapy. Physicians treating such patients should be alert to any revised recommendations from CDC for this group of patients.

Usual dose: Pyrazinamide is administered orally, 15 to 30 mg/kg once daily. Older regimens employed 3 or 4 divided doses daily, but most current recommendations are for once a day. Three grams per day should not be exceeded. The CDC recommendations do not exceed 2 g per day when given as a daily regimen (see table).

Alternatively, a twice weekly dosing regimen (50 to 75 mg/kg twice weekly based on lean body weight) has been developed to promote patient compliance with a regimen on an outpatient basis. In studies evaluating the twice weekly regimen, doses of pyrazinamide in excess of 3 g twice weekly have been administered. This exceeds the recommended maximum 3 g/daily dose. However, an increased incidence of adverse reactions has not been reported.

This table is taken from the CDC-American Thoracic Society joint recommendations. 4

Recommended Drugs for the Initial Treatment of Tuberculosis in Children and Adults

Drug

Daily Dose *

Children

Adults

Isoniazid

10 to 20 mg/kg

PO or IM

5 mg/kg

PO or IM

Rifampin

10 to 20 mg/kg

PO

10 mg/kg

PO

Pyrazinamide

15 to 30 mg/kg

PO

15 to 30 mg/kg

PO

Streptomycin

20 to 40 mg/kg

IM

15 mg/kg

IM

Ethambutol

  1. 15 to 25 mg/kg

PO

  1. 15 to 25 mg/kg

PO

Drug

Maximal Daily Dose in Children and Adults

Isoniazid

300 mg

Rifampin

600 mg

Pyrazinamide

2 g

Streptomycin

1 g **

Ethambutol

  1. 2.5 g

Drug

Twice Weekly Dose

Children

Adults

Isoniazid

20 to 40 mg/kg

Max. 900 mg

15 mg/kg

Max. 900 mg

Rifampin

10 to 20 mg/kg

Max. 600 mg

10 mg/kg

Max. 600 mg

Pyrazinamide

50 to 70 mg/kg

50 to 70 mg/kg

Streptomycin

25 to 30 mg/kg

IM

25 to 30 mg/kg

IM

Ethambutol

50 mg/kg

50 mg/kg

Definition of abbreviations: PO = perorally; IM = intramuscularly.

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