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What is the most important information I should know about isoniazid?

Take all of the isoniazid that has been prescribed for you even if you begin to feel better. Your symptoms may begin to improve before the infection is completely treated. Avoid alcohol while taking isoniazid. Alcohol may increase the risk of damage to the liver during isoniazid treatment.

Contact your doctor immediately if you experience numbness or tingling in the hands or feet, weakness, fatigue, loss of appetite, nausea and vomiting, yellowing of the skin or eyes, or darkening of the urine.

What is isoniazid?

Isoniazid is an antibiotic. It prevents tuberculous bacteria from multiplying in the body.

Isoniazid is used to treat and to prevent tuberculosis (TB).

Isoniazid may also be used for purposes other than those listed in this medication guide.

What should I discuss with my healthcare provider before taking isoniazid?

Before taking this medication, tell your doctor if you have

• ever had an allergic reaction to isoniazid,

• kidney disease, or

• liver disease.

You may not be able to take isoniazid, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.

It is not known whether isoniazid will be harmful to an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant or could become pregnant during treatment. It is not known whether isoniazid will be harmful to a nursing baby. Do not take this medication without first talking to your doctor if you are breast-feeding a baby.

How should I take isoniazid?

Take isoniazid exactly as directed by your doctor. If you do not understand these instructions, ask your pharmacist, nurse, or doctor to explain them to you.

Take each dose with a full glass (8 ounces) of water. Take isoniazid on an empty stomach 1 hour before or 2 hours after meals.

If nausea occurs, ask your doctor if you can take isoniazid with food.

Take all of the isoniazid that has been prescribed for you even if you begin to feel better. Your symptoms may begin to improve before the infection is completely treated.

It is important to take isoniazid regularly to get the most benefit.

Your doctor may also want you to take a supplemental vitamin B6 (pyridoxine) tablet daily during treatment to prevent numbness and tingling caused by low levels of this vitamin.

Your doctor may want you to have blood tests or other medical evaluations during treatment with isoniazid to monitor progress and side effects.

Store this medication at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. If it is almost time for the next regularly scheduled dose, skip the missed dose and take the next one as directed. Do not take a double dose of this medication.

What happens if I overdose?

Seek emergency medical attention if an overdose is suspected.

Symptoms of an isoniazid overdose include nausea, vomiting, dizziness, slurring of speech, blurred vision, visual hallucinations, seizures, coma, and death.