Isoniazid
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Drug Status
Government Approvals
US(FDA), UK(BNF)
WHO Essential Medicine
NO
Known Teratogen
No
Pharmaceutical Class
Antimycobacterial
Controlled Drug Substance
No
isoniazid
Summary
Isoniazid is used to treat tuberculosis, which is a bacterial infection affecting the lungs. It helps kill the bacteria causing the disease, reducing symptoms like cough and fever. It's also used for latent tuberculosis infection, which is when the bacteria are present but not causing symptoms, to prevent the development of active disease.
Isoniazid works by inhibiting the synthesis of mycolic acids, which are essential components of the bacterial cell wall in tuberculosis bacteria. This action disrupts the cell wall, effectively killing the bacteria and helping to clear the infection.
The usual starting dose of Isoniazid for adults is 300 mg once daily, taken on an empty stomach. For children, the dose is typically adjusted based on their weight. It's important to follow your doctor's specific dosing instructions to ensure the medication is effective and safe.
Common side effects of Isoniazid include nausea, vomiting, and mild liver enzyme changes. Some people may experience numbness or tingling in the hands and feet, known as peripheral neuropathy, which is nerve damage causing these sensations.
Isoniazid can cause liver damage, especially in people over 35, those with a history of liver disease, or those who drink alcohol regularly. It's contraindicated in people with a known allergy to it or its ingredients and those with severe liver disease.
Indications and Purpose
How does Isoniazid work?
Isoniazid works by inhibiting the synthesis of mycolic acids, which are essential components of the bacterial cell wall in tuberculosis bacteria. Think of it like removing the bricks from a wall, causing it to collapse. By disrupting the cell wall, Isoniazid kills the bacteria, helping to clear the infection. This action makes it effective in treating tuberculosis, which is a bacterial infection affecting the lungs. It's often used with other medications to ensure effective treatment.
Is Isoniazid effective?
Yes, Isoniazid is effective in treating tuberculosis, which is a bacterial infection that primarily affects the lungs. It works by killing the bacteria that cause the disease. Clinical studies and decades of use have shown that Isoniazid significantly reduces the risk of developing active tuberculosis in people with latent infection. It is often used in combination with other medications to ensure the best outcomes and prevent the development of drug-resistant strains.
What is Isoniazid?
Isoniazid is an antibiotic used to treat tuberculosis, which is a bacterial infection affecting the lungs. It belongs to the class of medicines called antitubercular agents. Isoniazid works by killing the bacteria that cause tuberculosis, helping to clear the infection. It's often used in combination with other medications to ensure effective treatment and prevent the development of drug-resistant strains. It's important to follow your doctor's instructions when taking Isoniazid.
Directions for Use
For how long do I take Isoniazid?
Isoniazid is usually taken for a long-term period to treat tuberculosis, which is a bacterial infection. The typical duration is 6 to 9 months, depending on your doctor's recommendation and your response to treatment. It's important to complete the full course to ensure the infection is fully treated and to prevent drug resistance. Always follow your doctor's instructions regarding the duration of your treatment.
How do I dispose of Isoniazid?
To dispose of Isoniazid, take it to a drug take-back program or collection site at a pharmacy or hospital. They will dispose of it properly to prevent harm to people or the environment. If you can't find a take-back program, you can throw it in the trash at home. First, mix it with something undesirable like used coffee grounds, seal it in a plastic bag, and then throw it away. Always keep it out of reach of children.
How do I take Isoniazid?
Take Isoniazid once daily, preferably on an empty stomach, either one hour before or two hours after meals. If you have trouble swallowing the pill, it can be crushed. Avoid alcohol while on this medication, as it can increase the risk of liver damage. If you miss a dose, take it as soon as you remember, unless it's almost time for your next dose. In that case, skip the missed dose and continue with your regular schedule. Never take two doses at once. Always follow your doctor's specific instructions.
How long does it take for Isoniazid to start working?
Isoniazid starts working soon after you begin taking it, but you may not notice all the benefits right away. For tuberculosis, which is a bacterial infection, symptoms like cough and fever may improve within a few weeks. However, the full therapeutic effect can take several months. It's important to complete the entire course of treatment to ensure the infection is fully cleared and to prevent drug resistance. Always follow your doctor's instructions.
How should I store Isoniazid?
Store Isoniazid at room temperature, away from moisture and light. Keep it in a tightly closed container to protect it from damage. Avoid storing it in humid places like bathrooms, as moisture can affect its effectiveness. Always keep it out of reach of children to prevent accidental ingestion. Check the expiration date regularly and properly dispose of any unused or expired medication.
What is the usual dose of Isoniazid?
The usual starting dose of Isoniazid for adults is 300 mg once daily. It can be taken with or without food. For children, the dose is typically adjusted based on their weight. The maximum recommended dose for adults is 300 mg per day. Dose adjustments may be necessary for people with liver problems or the elderly. Always follow your doctor's specific dosing instructions to ensure the medication is effective and safe for your health needs.
Warnings and Precautions
Can Isoniazid be taken safely while breastfeeding?
Isoniazid is considered safe to use while breastfeeding. It does pass into breast milk, but the amounts are generally low and not expected to harm the nursing infant. However, it's important to monitor the baby for any unusual symptoms, such as jaundice, which is yellowing of the skin or eyes. Always discuss with your doctor before starting Isoniazid while breastfeeding to ensure it's the best option for you and your baby.
Can Isoniazid be taken safely while pregnant?
Isoniazid is generally considered safe during pregnancy, but it should only be used when clearly needed. The benefits of treating tuberculosis, which is a serious infection, usually outweigh the risks. Your doctor will weigh the potential benefits and risks before prescribing it. If you are pregnant or planning to become pregnant, discuss your treatment options with your doctor to ensure the best outcome for you and your baby.
Can I take Isoniazid with other prescription drugs?
Isoniazid can interact with several medications, increasing the risk of side effects or reducing effectiveness. Major interactions include phenytoin, which is used for seizures, and warfarin, which is a blood thinner. These interactions can increase the risk of toxicity or bleeding. Isoniazid can also interact with alcohol, increasing the risk of liver damage. Always inform your doctor about all medications you are taking to avoid potential interactions and ensure safe treatment.
Does Isoniazid have adverse effects?
Adverse effects are unwanted reactions to a medication. Common adverse effects of Isoniazid include liver damage, peripheral neuropathy, which is nerve damage causing numbness or tingling, and gastrointestinal issues like nausea. Serious side effects can include severe liver damage and allergic reactions. If you notice symptoms like yellowing of the skin or eyes, severe fatigue, or rash, contact your doctor immediately. Regular monitoring and communication with your healthcare provider can help manage these effects.
Does Isoniazid have any safety warnings?
Yes, Isoniazid has important safety warnings. It can cause liver damage, especially in people over 35, those with a history of liver disease, or those who drink alcohol regularly. Symptoms of liver damage include fatigue, weakness, loss of appetite, nausea, vomiting, and yellowing of the skin or eyes. If you experience these symptoms, contact your doctor immediately. Regular liver function tests are recommended while taking Isoniazid to monitor for potential liver issues.
Is Isoniazid addictive?
Isoniazid is not addictive or habit-forming. It does not cause dependency or withdrawal symptoms when you stop taking it. Isoniazid works by killing bacteria that cause tuberculosis, and it does not affect brain chemistry in ways that could lead to addiction. You won't experience cravings for this medication or feel compelled to take more than prescribed. If you have concerns about medication dependence, you can feel confident that Isoniazid doesn't carry this risk.
Is Isoniazid safe for the elderly?
Elderly individuals are more vulnerable to the side effects of Isoniazid, particularly liver damage. This is because liver function can decline with age, increasing the risk of adverse effects. Regular monitoring of liver function is important for elderly patients taking Isoniazid. If you are older and prescribed this medication, your doctor will likely conduct frequent check-ups to ensure your safety and adjust the treatment as needed.
Is it safe to drink alcohol while taking Isoniazid?
It's best to avoid alcohol while taking Isoniazid. Alcohol can increase the risk of liver damage, which is a serious side effect of this medication. Drinking alcohol can also worsen other side effects like dizziness or nausea. If you choose to drink, limit your intake and watch for symptoms like fatigue, yellowing of the skin or eyes, or dark urine. These could indicate liver problems and require immediate medical attention. Always talk with your doctor about alcohol use while on Isoniazid.
Is it safe to exercise while taking Isoniazid?
Yes, you can exercise while taking Isoniazid, but listen to your body. Some people may experience side effects like dizziness or fatigue, which could affect exercise capacity. If you feel dizzy or unusually tired, take a break and rest. Stay hydrated and avoid strenuous activities if you're not feeling well. Most people can maintain their regular exercise routine, but consult your doctor if you have concerns about your specific situation.
Is it safe to stop Isoniazid?
It's important not to stop Isoniazid without consulting your doctor. This medication is usually taken for a specific duration to effectively treat tuberculosis. Stopping it early can lead to incomplete treatment and the development of drug-resistant bacteria. If you experience side effects or have concerns, talk to your doctor. They can help adjust your treatment plan safely. Always follow your doctor's advice to ensure the best outcome for your health.
What are the most common side effects of Isoniazid?
Side effects are unwanted reactions to a medication. Common side effects of Isoniazid include nausea, vomiting, and mild liver enzyme changes. These occur in a small percentage of people. Some may experience numbness or tingling in the hands and feet, known as peripheral neuropathy. If you notice new symptoms after starting Isoniazid, they might be temporary or unrelated to the medication. Always talk with your doctor before stopping any medication.
Who should avoid taking Isoniazid?
Isoniazid should not be used by people with a known allergy to it or its ingredients. It's also contraindicated in those with severe liver disease, as it can cause liver damage. Caution is needed for people with a history of alcohol abuse or those over 35, as they have a higher risk of liver problems. Always consult your doctor about your medical history before starting Isoniazid to ensure it's safe for you.
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