Isoniazid Tablet Tablet (Isoniazid) — Uses, Dosage & NAFDAC

Who is this for?

What is this drug?

Isoniazid is an antibiotic specifically designed to fight tuberculosis (TB) bacteria. It works by stopping the TB germs from building their protective walls, which kills them off over time.

What is it used for?

Tuberculosis (TB)TB prevention in people exposed to someone with active TBlatent TB infection (when you carry the TB germ but are not yet sick)

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Tuberculosis (TB)

Prescription Required

You need a doctor's prescription to buy this drug.

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How to take this drug

For active TB treatment, the usual adult dose is 300 mg (one 300 mg tablet) taken once daily on an empty stomach — ideally 1 hour before food or 2 hours after eating. Your doctor will combine it with other TB drugs. For TB prevention, the dose is also 300 mg once daily, usually for 6 to 9 months. Always follow your doctor's exact instructions and never stop early even if you feel better.

What if I Miss a Dose?

If you miss a dose, take it as soon as you remember. But if it is almost time for your next dose, skip the missed one and continue your normal schedule. Do not take two doses at once to make up for it.

Important for antibiotics

Always complete the full course even if you feel better. Stopping early can cause the infection to return and become drug-resistant.

What to watch out for

Complete your full TB treatment course even if you feel fine — stopping early can cause drug-resistant TB which is much harder and more expensive to treat. Your doctor may prescribe vitamin B6 (pyridoxine) alongside isoniazid to prevent nerve problems — make sure you take it. Only buy your isoniazid from licensed pharmacies and not from roadside sellers, as fake or expired TB drugs are dangerous and can make the disease harder to cure.

Common Side Effects

Tingling or numbness in the hands and feet
mild nausea or stomach upset
feeling tired or weak
loss of appetite
mild skin rash

Serious Side Effects

Yellowing of the eyes or skin (jaundice) which signals liver damage — stop the drug and go to the hospital immediately. Severe stomach pain
dark-coloured urine
or unusual bleeding
which may also indicate liver problems. Sudden vision changes or seizures require emergency medical attention.

Drug Interactions

Alcohol — drinking alcohol while on isoniazid greatly increases your risk of liver damage, so avoid alcohol completely during treatment. Paracetamol — using paracetamol regularly alongside isoniazid can also stress your liver, so use it sparingly and only when necessary. Antacids like aluminium hydroxide (commonly sold in Nigerian pharmacies) can reduce how well isoniazid works — take them at least 1 hour apart.

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Pregnancy & Breastfeeding Warning

Isoniazid can be used during pregnancy and breastfeeding when your doctor decides the benefit of treating or preventing TB outweighs the risks — always consult your doctor before taking it.

Who Should NOT Take This

People who have had a serious allergic reaction to isoniazid before
anyone with active liver disease or a history of isoniazid-related liver damage
heavy alcohol drinkers with liver problems
and people with a history of severe drug-induced hepatitis.

How to Store

Store in a cool, dry place away from direct sunlight and heat — Nigerian weather can be very hot, so avoid storing it near windows or in your car. Keep the container tightly closed to protect from moisture, and always keep it out of the reach of children.

For information only — not medical advice. Always talk to a doctor or pharmacist before changing your medication.

Isoniazid Tablet