Isoniazid

Brand names

• Dom-Isoniazid
• Isotamine
• Laniazid
• Nydrazid
• P-I-N Forte [CD]
• PMS-Isoniazid
• Rifamate [CD]
• Rifater [CD]
• Seromycin w/Isoniazid [CD]
• Teebaconin

Usage

To prevent and treat tuberculosis (TB). It may be taken alone to prevent TB, but must be used with other antitubercular agents to treat an active case of TB.

How it works

Isoniazid interferes with the formation of DNA and lipids, needed to manufacture the TB bacteria's cell walls.

Side effects

Serious

Numbness, pain, burning, or tingling in hands and feet; loss of appetite; stomach pain; clumsiness; yellowish tinge to the eyes or skin; nausea; vomiting; darkened urine; unusual fatigue. Call your doctor immediately.

Common

Diarrhea, rash, fever.

Less common

Irritability, seizures.

Possible interactions

Other medicaments:

Isoniazid may increase the effects of:

• carbamazepine (Tegretol) and cause toxicity.
• disulfiram (Antabuse) and change behavior.
• phenytoin (Dilantin) or fosphenytoin (Cerebyx) and cause toxicity.

The following medicaments may decrease the effects of isoniazid:



• cortisonelike medicaments.

Isoniazid taken concurrently with:



• acetaminophen (Tylenol) may increase the risk of liver toxicity.
• antacids may decrease the absorption of this medicine. Separate antacid dosing by 2 hours from dosing of this medicine.
• BCG vaccine will result in decreased vaccine effectiveness.
• cyclosporine (Sandimmune) may blunt cyclosporine benefits.
• diazepam and perhaps other benzodiazepines may result in increased blood levels and toxicity.
• ketoconazole, itraconazole or related compounds may result in decreased therapeutic benefits of the antifungal.
• meperidine (Demerol) may result in excessive lowering of blood pressure.
• niacin (various) may lead to a need for increased niacin.
• oral antidiabetic medicaments may result in loss of control of blood glucose.
• propranolol (Inderal, others) may lead to isoniazid toxicity.
• rifampin (Rifadin, others) can result in a serious increased risk of liver toxicity.
• theophylline (Theodur, others) may result in theophylline toxicity.
• valproic acid (Depakene) can result in isoniazid or valproic acid toxicity.
• warfarin (Coumadin) may result in increased bleeding risk; more frequent INR (prothrombin time or protime) testing is needed.

Foods:

Eat the following foods cautiously until your tolerance is determined: Swiss and Cheshire cheeses, tuna fish, skipjack fish and Sardinella species. These may interact with the medicament to produce skin rash, itching, sweating, chills, headache, light-headedness or rapid heart rate. Taking this medicament with food also acts to decrease absorption and lessen therapeutic benefits. Some red wines and aged cheeses also contain high levels of tyramine. This may result in an undesirable increase in blood pressure if consumed. Avoid this combination.

Herbal medicines or minerals:

Echinacea: some patients use Echinacea to attempt to boost their immune systems. Unfortunately, use of Echinacea is not recommended in people with damaged immune systems. This herb may also actually weaken any immune system if it is used too often or for too long a time. Do not take mistletoe herb, oak bark or marshmallow root and licorice.

Alcohol:

Alcohol may reduce the effectiveness of this medicament and increase the risk of liver toxicity.

Discontinuation:

Long-term treatment is required. Do not stop this medicament without asking your physician.