Sep, 21 2025
Isoniazid: Complete Guide to Uses, Dosage, Side Effects & Safety
A thorough, up‑to‑date look at Isoniazid-what it treats, how it works, proper dosing, common side effects, and practical tips for patients and clinicians.
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Isoniazid is a medicine used to treat and prevent tuberculosis (TB). It works by killing the bacteria that cause TB, mainly in the lungs. Doctors often prescribe it as part of a combo of drugs because TB can become resistant if only one medicine is used.
When you start Isoniazid, you’ll usually take it once a day, with or without food. The exact dose depends on your weight, age, and liver health. For most adults, the usual dose is 300 mg daily, but kids and people with liver problems may get a lower amount.
Stick to the schedule your doctor gave you. Missing doses can let the bacteria bounce back and make the infection harder to clear. If you forget a dose, take it as soon as you remember—unless it’s almost time for the next one. In that case, skip the missed dose and keep going with your regular schedule. Don’t double‑up.
Many people take a vitamin B6 supplement (pyridoxine) alongside Isoniazid. This helps prevent nerve problems that can happen with the drug. Ask your doctor if you need it and how much to take.
Before you start, your doctor will probably check your liver enzymes. Isoniazid can irritate the liver, so these tests are a baseline. While you’re on the medicine, you may need a follow‑up blood test after a month and then every few months.
Most folks feel fine, but some notice side effects. The most common are mild stomach upset and a slight headache. If you get a rash, fever, or yellow skin (signs of liver trouble), call your doctor right away.
Nerve pain or tingling in the hands and feet can also show up, especially if you skip the B6 supplement. Taking the recommended pyridoxine dose usually stops this.
Isoniazid can interact with a few other drugs. Alcohol can make liver irritation worse, so limit or avoid it while you’re on treatment. Some seizure medicines, certain antibiotics, and the HIV drug zidovudine may need dose adjustments. Always share your full medication list with your pharmacist.
If you’re pregnant or planning a baby, discuss Isoniazid with your doctor. The drug is generally considered safe, but you’ll still need close monitoring.
When the full course finishes—usually six months for active TB or nine months for preventive therapy—your doctor will confirm the infection is gone with a chest X‑ray or a sputum test. Don’t stop early even if you feel better.
Bottom line: Isoniazid is a cornerstone of TB treatment, but it works best when you follow dosing instructions, take B6 if needed, and keep an eye on liver health. If you have any doubts, a quick call to your healthcare provider can keep you on track and avoid complications.
Sep, 21 2025
A thorough, up‑to‑date look at Isoniazid-what it treats, how it works, proper dosing, common side effects, and practical tips for patients and clinicians.