Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For isoniazid and thiacetazone combination, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to isoniazid or thiacetazone. Also tell your health care worker if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Isoniazid has not been shown to cause birth defects or other problems in humans and has not been shown to cause birth defects in animals. Studies in rats and rabbits have shown that isoniazid may increase the risk of miscarriage. However, tuberculosis is a very serious disease and many women have been treated with isoniazid during pregnancy with no problems occurring in their babies. Studies on the effects of thiacetazone in pregnancy have not been done in humans or animals.

Breast-feeding—Isoniazid passes into the breast milk. However, isoniazid has not been reported to cause problems in nursing babies. Also, there is not enough isoniazid in breast milk to protect or treat babies who have been exposed to tuberculosis. It is not known whether thiacetazone passes into breast milk.

Children—Isoniazid and thiacetazone combination can cause serious side effects in any patient. Therefore, it is especially important that you discuss with the child's doctor the good that this medicine may do as well as the risks of using it.

Older adults—Hepatitis may be especially likely to occur in older patients, who are usually more sensitive than younger adults to the effects of isoniazid.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking isoniazid and thiacetazone combination, it is especially important that your health care worker know if you are taking any of the following:

• Acetaminophen (e.g., paracetamol, Tylenol) (with long-term, high-dose use) or
• Amiodarone (e.g., Cordarone) or
• Anabolic steroids (nandrolone [e.g., Anabolin], oxandrolone [e.g., Anavar], oxymetholone [e.g., Anadrol], stanozolol [e.g., Winstrol]) or
• Androgens (male hormones) or
• Antithyroid agents (medicine for overactive thyroid) or
• Carmustine (e.g., BiCNU) or
• Chloroquine (e.g., Aralen) or
• Dantrolene (e.g., Dantrium) or
• Daunorubicin (e.g., Cerubidine) or
• Divalproex (e.g., Depakote) or
• Estrogens (female hormones) or
• Etretinate (e.g., Tegison) or
• Gold salts (medicine for arthritis) or
• Hydroxychloroquine (e.g., Plaquenil) or
• Mercaptopurine (e.g., Purinethol) or
• Methotrexate (e.g., Mexate) or
• Methyldopa (e.g., Aldomet) or
• Naltrexone (e.g., Trexan) (with long-term, high-dose use) or
• Oral contraceptives (birth control pills) containing estrogen or
• Other anti-infectives by mouth or by injection (medicine for infection) or
• Phenothiazines (acetophenazine [e.g., Tindal], chlorpromazine [e.g., Thorazine], fluphenazine [e.g., Prolixin], mesoridazine [e.g., Serentil], perphenazine [e.g., Trilafon], prochlorperazine [e.g., Compazine], promazine [e.g., Sparine], promethazine [e.g., Phenergan], thioridazine [e.g., Mellaril], trifluoperazine [e.g., Stelazine], triflupromazine [e.g., Vesprin], trimeprazine [e.g., Temaril]) or
• Plicamycin (e.g., Mithracin) or
• Rifampin (e.g., Rifadin) or
• Valproic acid (e.g., Depakene)—These medicines may increase the chance of liver damage if taken with isoniazid and thiacetazone combination

• Carbamazepine (e.g., Tegretol) or
• Phenytoin (e.g., Dilantin)—These medicines may increase the chance of liver damage if taken with isoniazid and thiacetazone combination. There may also be an increased chance of side effects of carbamazepine and phenytoin

• Disulfiram (e.g., Antabuse)—Use of this medicine with isoniazid and thiacetazone combination may increase the chance of liver damage and side effects, such as dizziness, lack of coordination, irritability, and trouble in sleeping

• Ketoconazole (e.g., Nizoral)—Use of ketoconazole with isoniazid and thiacetazone combination can lower the blood levels of ketoconazole decreasing its effects

Other medical problems—The presence of other medical problems may affect the use of isoniazid and thiacetazone combination. Make sure you tell your doctor if you have any other medical problems, especially:

• Alcohol abuse (or history of) or
• Liver disease—There may be an increased chance of hepatitis with daily drinking of alcohol or in patients with liver disease

• Human immunodeficiency virus (HIV) infection—There may be an increased chance of severe skin rash in patients with HIV infection

• Kidney disease (severe)—There may be an increased chance of side effects in patients with severe kidney disease

• Seizure disorders such as epilepsy—There may be an increased chance of seizures (convulsions) in some patients