Isoniazid (Systemic)

Brand Names : Laniazid, Nydrazid, Isotamine, PMS Isoniazid, INH

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, the following should be considered:

Allergies - Tell your doctor if you have ever had any unusual or allergic reaction to isoniazid, ethionamide (e.g., Trecator-SC), pyrazinamide, or niacin (e.g., Nicobid, nicotinic acid). Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Diet - Make certain your health care professional knows if you are on a low-sodium, low-sugar, or any other special diet. Most medicines contain more than just the active ingredient, and many liquid medicines contain alcohol.

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

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.

Children - Isoniazid 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 patients over 50 years of age, 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 or receiving isoniazid it is especially important that your health care professional know if you are taking any of the following:

• Acetaminophen (e.g., Tylenol) (with long-term, high-dose use) or
• Alfentanil (e.g., Alfenta) 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
• Disulfiram (e.g., Antabuse) 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
• 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
• Valproic acid (e.g., Depakene) - These medicines may increase the chance of liver damage if taken with isoniazid

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

• Disulfiram (e.g., Antabuse) - This medicine 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) or
• Rifampin (e.g., Rifadin) - Use of these medicines with isoniazid can lower the blood levels of ketoconazole or rifampin, decreasing their effects

Other medical problems - The presence of other medical problems may affect the use of isoniazid. 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

• 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