April 27, 2017
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(rifampin, isoniazid and pyrazinamide USP) Tablets


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 age related. Approximate case rates by age are: 0 per 1,000 for persons under 20 years of age, 3 per 1,000 for persons in the 20 to 34 year age group, 12 per 1,000 for persons in the 35 to 49 year age group, 23 per 1,000 for persons in the 50 to 64 year age group, and 8 per 1,000 for persons over 65 years of age. The risk of hepatitis is increased with daily consumption of alcohol. Precise data to provide a fatality rate for isoniazid-related hepatitis is not available; however, in a U.S. Public Health Service Surveillance Study of 13,838 persons taking isoniazid, there were 8 deaths among 174 cases of hepatitis.

Therefore, patients given isoniazid should be carefully monitored and interviewed at monthly intervals. Serum transaminase concentration becomes elevated in about 10% to 20% of patients, usually during the first few months of therapy, but it can occur at any time. Usually enzyme levels return to normal despite continuance of drug, but in some cases progressive liver dysfunction occurs. Patients should be instructed to report immediately any of the prodromal symptoms of hepatitis, such as fatigue, weakness, malaise, anorexia, nausea, or vomiting. If these symptoms appear or if signs suggestive of hepatic damage are detected, isoniazid should be discontinued promptly since continued use of the drug in these cases has been reported to cause a more severe form of liver damage.

Patients with tuberculosis should be given appropriate treatment with alternative drugs. If isoniazid must be reinstituted, it should be reinstituted only after symptoms and laboratory abnormalities have cleared. The drug should be restarted in very small and gradually increasing doses and should be withdrawn immediately if there is any indication of recurrent liver involvement. Treatment should be deferred in persons with acute hepatic diseases.


RIFATER (rifampin/isoniazid/pyrazinamide USP) tablets are combination tablets containing 120 mg rifampin, 50 mg isoniazid, and 300 mg pyrazinamide for use in antibacterial therapy. The tablets also contain as inactive ingredients: povidone, carboxymethylcellulose sodium, calcium stearate, sodium lauryl sulfate, sucrose, talc, acacia, titanium dioxide, kaolin, magnesium carbonate, colloidal silicon dioxide, dried aluminum hydroxide gel, ferric oxide, black iron oxide, carnauba wax, white beeswax, colophony, hard paraffin, lecithin, shellac, and propylene glycol. The RIFATER triple therapy combination was developed for dosing convenience.


Rifampin is a semisynthetic antibiotic derivative of rifamycin SV. Rifampin is a red-brown crystalline powder very slightly soluble in water at neutral pH, freely soluble in chloroform, soluble in ethyl acetate and methanol. Its molecular weight is 822.95 and its chemical formula is C43H58N4O12. The chemical name for rifampin is either:

3-[[(4-methyl-1-piperazinyl) imino]-methyl]-rifamycin; or 5,6,9,17,19,21-hexahydroxy-23methoxy-2,4,12,16,18,20,22 heptamethyl-8-[N-(4-methyl-1-piperazinyl) formimidoyl]-2,7-(epoxypentadeca [1,11,13]trienimino)naphtho[2,1-b]furan-1, 11(2H)-dione 21-acetate. Its structural formula is:

Rifampin Structural Formula Illustration


Isoniazid is the hydrazide of isonicotinic acid. It is a colorless or white crystalline powder or white crystals. It is odorless and slowly affected by exposure to air and light. It is freely soluble in water, sparingly soluble in alcohol and slightly soluble in chloroform and in ether. Its molecular weight is 137.14 and its chemical formula is C6H7N3O.

The chemical name for isoniazid is 4-pyridinecarboxylic acid, hydrazide and its structural formula is:

Isoniazid Structural Formula Illustration


Pyrazinamide, the pyrazine analogue of nicotinamide, is a white, crystalline powder, stable at room temperature, and sparingly soluble in water. The chemical name for pyrazinamide is pyrazinecarboxamide and its molecular weight is 123.11. Its chemical formula is C5H5N3O and its structural formula is:

Pyrazinamide Structural Formula Illustration

What are the possible side effects of isoniazid, pyrazinamide, and rifampin (Rifater)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Isoniazid, pyrazinamide, and rifampin can cause severe liver symptoms. Stop taking this medication and call your doctor at once if you have any of these liver symptoms:

  • low fever;
  • nausea, stomach pain, loss of appetite;
  • dark urine, clay-colored stools; or
  • jaundice (yellowing of the skin or eyes).

Call your doctor at once if you have any other...

Read All Potential Side Effects and See Pictures of Rifater »

What are the precautions when taking rifampin, isoniazid and pyrazinamide (Rifater)?

See also Warning section.

Before taking this product, tell your doctor or pharmacist if you are allergic to rifampin, isoniazid, or pyrazinamide; or to other rifamycins (such as rifabutin, rifapentine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: previous severe reaction from isoniazid (such as liver disease), liver disease, kidney disease, alcohol use, HIV infection, diabetes, gout, high uric acid level in the blood, numbness/tingling of arms/legs (peripheral neuropathy), recent childbirth, a certain blood disorder (porphyria).


Read All Potential Precautions of Rifater »

Last reviewed on RxList: 1/31/2017
This monograph has been modified to include the generic and brand name in many instances.

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