Isoniazid
About Isoniazid
The prescription medicine Isoniazid is an oral treatment used to prevent and treat tuberculosis (TB), a serious bacterial infection that primarily affects the lungs. It works by stopping the growth of the bacteria responsible for this infection. This medication is a cornerstone of tuberculosis therapy and is vital for completely clearing the infection from your body.
For it to be fully effective, you must take Isoniazid consistently every day exactly as prescribed, even if you begin to feel better. It is best taken on an empty stomach, either one hour before or two hours after a meal, to ensure your body absorbs the medicine properly. Avoiding alcohol and eating a balanced diet rich in essential nutrients can also support your recovery and protect your body during treatment.
While taking this medicine, some people may experience mild side effects like numbness or tingling in the hands and feet. You should contact your doctor immediately if you notice serious signs of liver irritation, such as yellowing of your skin or eyes, dark urine, or unusual tiredness.
Before starting Isoniazid, tell your doctor if you have a history of liver disease, kidney issues, or nerve problems. Do not take this if you have previously experienced severe liver damage, active liver disease, or serious allergic reactions associated with this medicine.
This medicine can interact with alcohol, which significantly increases your risk of liver damage, as well as certain medications used to treat seizures. If you are pregnant, breastfeeding, or an older adult, talk to your doctor or pharmacist to discuss the risks and benefits before starting treatment.
Uses of Isoniazid
Medicinal Benefits
Isoniazid helps treat and prevent tuberculosis by eliminating or stopping the growth of the bacteria responsible for the infection. By controlling the infection, it supports recovery, reduces the risk of disease progression, and helps protect others from transmission.
- Helps Treat Tuberculosis Effectively: By targeting the bacteria that cause tuberculosis, Isoniazid helps clear the infection, relieving symptoms and supporting a successful recovery when used as part of the prescribed treatment regimen.
- Helps Prevent Active Tuberculosis: In individuals with latent tuberculosis infection, Isoniazid helps stop the bacteria from multiplying, reducing the risk of developing active tuberculosis disease.
- Supports Long-Term Health and Infection Control: By effectively controlling tuberculosis bacteria, Isoniazid helps prevent disease progression, lowers the risk of spreading the infection to others, and supports better long-term health outcomes when taken as prescribed.
Directions for Use
- Isoniazid should be taken on an empty stomach, at least 1 hour before or 2 hours after a meal.
- Your doctor will determine the dosage and timing of this medication based on your body weight and medical condition.
- Swallow Isoniazid as a whole with a glass of water.
- Do not crush, break, or chew it.
Storage
Side Effects of Isoniazid
Common Side Effects (Usually mild):
- Numbness, tingling, or a 'pins and needles' feeling in your hands or feet
- Mild nausea or stomach discomfort
- Loss of appetite
Serious Side Effects (Consult a doctor right away):
- Signs of liver problems, such as yellowing of the skin or eyes (jaundice), unusually dark urine, severe stomach pain, or persistent nausea and vomiting
- Severe allergic reactions, including skin rash, itching, swelling of the face, lips, or throat, or difficulty breathing
- Unusual bruising or bleeding
- Changes in vision or eye pain
Medicines Containing this Salt
View AllDrug Warnings
- Get regular blood tests as recommended by your doctor to monitor your liver function while taking this medicine.
- Avoid taking antacids containing aluminium within 2 hours of taking your medication, as they can prevent your body from absorbing it.
- Watch closely for early signs of liver irritation, such as unexplained fatigue, weakness, or loss of appetite, and report them to your doctor immediately.
- Do not share this medication with anyone else, even if they have the same symptoms as you.
Drug Interactions
- May increase the levels and side effects of certain seizure medications (such as phenytoin or carbamazepine) when taken together.
- Taking this medicine with acetaminophen can increase the risk of liver damage.
- Antacids containing aluminium can lower the absorption of this medicine, making it less effective.
Drug-Drug Interactions Checker List:
Safety Advice
Alcohol
unsafeAvoid alcohol consumption while on treatment with Isoniazid as it may increase the risk of liver damage. Please consult your doctor if you have any concerns.
Pregnancy
safe if prescribedIf you are pregnant, consult your doctor before taking Isoniazid. Your doctor may prescribe this medicine if the benefits outweigh the risks.
Breast Feeding
safe if prescribedIsoniazid is excreted in breast milk in low quantities. If you are breastfeeding, consult your doctor before taking Isoniazid. Your doctor may prescribe this medicine if the benefits outweigh the risks.
Driving
unsafeIsoniazid may cause mental health problems, fits or optic neuritis (swelling of the optic nerve that may cause vision loss) in some people. Therefore, avoid driving if you experience any of these symptoms after taking Isoniazid.
Liver
consult your doctorTake Isoniazid with caution, especially if you have a history of liver disease. Your doctor may adjust the dose of this medicine or prescribe a suitable alternative based on your condition.
Kidney
consult your doctorTake Isoniazid with caution, especially if you have a history of kidney disease. Your doctor may adjust the dose of this medicine or prescribe a suitable alternative based on your condition.
Children
cautionIsoniazid is not recommended for children below 3 months of age. However, in children above 3 months, Isoniazid should be used under medical supervision.
Habit Forming
Diet & Lifestyle Advise
- Avoid alcohol completely while taking this medicine, as the combination significantly increases your risk of severe liver damage.
- Avoid foods high in tyramine and histamine, such as aged cheeses, red wine, cured meats, yeast extracts, and certain fish like tuna, because combining them with this medicine can cause sudden high blood pressure, sweating, flushing, or a fast heartbeat.
- Ask your doctor about taking a daily pyridoxine (Vitamin B6) supplement, as this helps prevent the nerve damage (numbness and tingling) that can sometimes occur during treatment.
- Eat a nutritious, balanced diet to help support your immune system as your body fights off the infection.
Special Advise
- Your doctor may recommend regular blood tests while you are taking Isoniazid to monitor your liver function.
- Consult a pulmonologist or lung specialist if you have had a persistent cough for three weeks or longer, chest pain, or coughing up blood or sputum from deep within the lungs.
- A monthly liver function test is advisable while using Isoniazid.
Patients Concern
Disease/Condition Glossary
Tuberculosis (TB) is an infectious bacterial disease that primarily affects the lungs. Still, it can also spread to other parts of the body, including the kidneys, brain, spine, and bone marrow. Tuberculosis is caused by a bacterium named Mycobacterium tuberculosis. It is a contagious disease that can spread to others through small droplets released into the air by a person with tuberculosis. Symptoms include a persistent cough lasting several weeks, chest pain while coughing or during normal breathing, unexplained fatigue, fever, night sweats, loss of appetite, and unintentional weight loss. People who smoke or consume alcohol, people diagnosed with HIV, and those with immune system problems are more likely to develop active TB.
FAQs
Isoniazid is used to treat and prevent tuberculosis (TB).
Isoniazid contains isoniazid, an antibiotic used to treat and prevent tuberculosis. Isoniazid prevents bacteria from producing mycolic acids, which are required to form cell walls (protective coating). Additionally, Isoniazid may combine with an enzyme that interferes with bacterial cell metabolism. Bacteria die due to the disruption in their metabolism and the lack of a cell wall. As a result, it kills Mycobacterium tuberculosis bacteria that cause tuberculosis (TB) and eliminates the infection.
It is not recommended to take Isoniazid with food. You are advised to take Isoniazid on an empty stomach at least 1 hour before a meal or 2 hours after a meal for better absorption.
You are recommended to avoid foods and drinks containing histamine or tyramine such as cured meat, matured cheese, soya, tuna, salmon, mackerel, wine, and beer as they may interact with Isoniazid and cause adverse effects such as sweating, headache, dizziness, light-headedness, flushing (reddening of the skin), fainting due to low blood pressure, uneven, fast or forceful heartbeat.
Yes, Isoniazid may cause liver problems in some patients. However, please consult your doctor if you notice symptoms such as yellowing of eyes or skin, dark urine, pale stools, weakness, loss of appetite, nausea or vomiting. Your doctor may monitor your liver function while on treatment with Isoniazid.
You are advised to consult a doctor before taking phenytoin with Isoniazid, as taking these medicines together may increase the levels of phenytoin in the blood and cause toxic effects. However, if you experience dizziness, vomiting, confusion or nausea, please consult your doctor.
Please do not stop taking Isoniazid suddenly without consulting your doctor, as it may cause withdrawal symptoms such as irritation, nervousness, difficulty sleeping, headache or having more dreams. Therefore, take Isoniazid for as long as your doctor has prescribed it. If you experience any difficulty while taking Isoniazid, please consult your doctor.
Isoniazid is not recommended for patients experiencing seizures, as it may increase the risk of recurring seizures. Therefore, it is advised to inform your doctor if you have a history of fits before taking Isoniazid.
Inform your doctor if your symptoms persist or worsen after completing the full course of Isoniazid. If you notice any undesirable effects that bother you while taking Isoniazid, consult your doctor.
If you miss taking a dose of Isoniazid, then take it as soon as you remember. However, if it is time for the next dose, skip the missed dose and continue with the regular dose. Avoid taking a double dose to make up for the missed one.
Isoniazid may cause side effects such as fever, dizziness, nausea, stomach upset, loss of appetite, constipation, tiredness, and numbness in the feet or hands. Most of these side effects are temporary and do not require any medical attention, as they will gradually reduce over time. However, contact your doctor if the side effects persist or worsen.
No, you must avoid alcohol completely while taking this medication. Alcohol significantly increases the risk of serious liver damage during treatment. Talk to your doctor if you find it difficult to stop drinking.
Your doctor may prescribe pyridoxine (Vitamin B6) to help prevent nerve damage, which can cause numbness, tingling, or burning sensations in your hands and feet. Talk to your doctor or pharmacist about whether you need this supplement.
You should take this medicine on an empty stomach, either 1 hour before or 2 hours after a meal, as food can reduce how much of the drug your body absorbs. If you experience severe stomach upset, talk to your doctor.
Yellowing of your skin or eyes is a sign of jaundice, which indicates potential liver damage. Stop taking the medicine and contact your doctor immediately or seek emergency medical care.
No, you must complete the entire course of treatment exactly as prescribed by your doctor. Stopping early can allow the bacteria to survive, cause the infection to return, and make the bacteria resistant to treatment. Talk to your doctor if you have concerns about your treatment duration.
Yes, you should avoid foods rich in tyramine and histamine, such as aged cheeses, cured meats, red wine, yeast extracts, and certain fish like tuna or mackerel. Combining these with your medicine can cause flushing, sweating, headaches, or a dangerous spike in blood pressure. Talk to your doctor or pharmacist for a complete list.
If you are pregnant or planning to become pregnant, you must discuss the risks and benefits of this medicine with your doctor. It is often prescribed during pregnancy to treat active tuberculosis, but close medical monitoring and vitamin B6 supplementation are typically required.
In rare cases, this medicine can cause optic neuritis, which affects the nerves in your eyes and can cause changes in vision or eye pain. If you experience any changes in your sight, contact your doctor right away.
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