Isoniazid Prescription: What You Need to Know
If your doctor just wrote you a prescription for isoniazid, you might be wondering how it works and what to expect. Isoniazid is a cornerstone drug for treating tuberculosis (TB). It kills the bacteria that cause TB and helps prevent the disease from spreading.
How to Take Isoniazid Correctly
Take the tablet exactly as your doctor ordered, usually once a day on an empty stomach. Swallow it with a full glass of water – no crushing or chewing unless instructed otherwise. If you miss a dose, take it as soon as you remember but skip it if it's almost time for the next one. Consistency is key; stopping early can let TB come back stronger.
Typical Dosage and Duration
Adults generally start with 300 mg daily, while kids get a weight‑based dose (about 10–15 mg per kilogram). Treatment often lasts six to nine months, depending on your infection’s severity. Your doctor may combine isoniazid with other TB meds for the first two months – that’s called an intensive phase.
Because isoniazid can affect the liver, most doctors order a baseline liver function test and repeat it after a few weeks. If you notice yellowing of the skin or eyes, dark urine, or persistent nausea, call your doctor right away – those are signs of liver trouble.
Alcohol can raise the risk of liver damage, so limit drinking while on isoniazid. Also, tell your pharmacist about any other meds you take; certain drugs like rifampin and some anti‑seizure medicines can lower isoniazid levels, making it less effective.
Common side effects are mild: occasional headache, nausea, or a loss of appetite. If they’re brief, they usually go away on their own. However, if you develop a rash, fever, or joint pain, that could signal an allergic reaction – seek medical help promptly.
Pregnant women can safely use isoniazid, but only under close supervision because the drug crosses the placenta. Your doctor will weigh the benefits of treating TB against any potential risks to the baby.
To keep track of your therapy, write down each dose in a notebook or set a daily alarm on your phone. Having a routine helps you finish the full course and reduces the chance of drug‑resistant TB.
Finally, remember that isoniazid isn’t a cure for TB on its own – it works best as part of a combination regimen. Follow up with your healthcare provider for sputum tests or X‑rays to confirm the infection is clearing.
