This article describes possible side effects of isoniazid oral tablet. You can explore this overview article to learn more about isoniazid, including the drug’s uses, ways to save on cost, and more.
Isoniazid oral tablet is a generic medication. It isn’t available in a brand-name version.
Isoniazid also comes in injectable forms and an oral syrup, but these forms aren’t described in this article. To learn more about these forms, talk with your doctor.
Boxed warning: Risk of hepatitis
Isoniazid oral tablet has a boxed warning for hepatitis. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
For details, see the “Side effects of isoniazid in detail” section below.
Need a diagnosis or prescription quickly? For certain health conditions, Optum Perks offers personalized on-demand care with no appointment required. For $25, answer a few questions online and receive a diagnosis and treatment plan from a board certified healthcare professional in 15 minutes or less. Get started here.
More common side effects of isoniazid
Isoniazid oral tablet may cause mild or serious side effects. Below are some of the more common side effects of this medication.
Commonly reported side effects of isoniazid oral tablet include:
* To learn more about this side effect, see the “Side effects of isoniazid in detail” section below.
Mild side effects of isoniazid
Isoniazid may cause certain mild side effects. Typically, mild side effects are temporary and can be easily managed. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.
Mild side effects of isoniazid oral tablet that occurred in studies include:
Isoniazid oral tablet may cause more mild side effects than those listed above. For details, see the drug’s prescribing information.
* An allergic reaction is possible with isoniazid oral tablet. But it’s unclear whether it occurred in the drug’s studies. To learn more about this side effect, see the “Side effects of isoniazid in detail” section below.
Serious side effects of isoniazid
Isoniazid may cause certain serious side effects. If you have any serious side effects from isoniazid oral tablet, call your doctor right away. But if you think you’re having a medical emergency or your side effects feel life threatening, take immediate action. Call 911 or a local emergency number, or go to the nearest emergency room.
After the FDA approves a drug, it tracks and reviews side effects of the medication. Visit MedWatch’s website if you’d like to notify the FDA about a side effect you’ve had with isoniazid.
Serious side effects of isoniazid oral tablet that occurred in studies include:
* To learn more about this side effect, see the “Side effects of isoniazid in detail” section below.
† Isoniazid oral tablet has a boxed warning for this side effect. A boxed warning is the most serious warning from the FDA.
‡ An allergic reaction is possible with isoniazid oral tablet. But it’s unclear whether it occurred in the drug’s studies.
Download the free Optum Perks Discount Card to save up to 80% on some prescription medications.
Common questions about side effects of isoniazid
Here are answers to some common questions about side effects of isoniazid oral tablet. If you have other questions, talk with your doctor or pharmacist.
How do side effects of isoniazid compare with those seen with rifampin or pyrazinamide?
Side effects of isoniazid are similar to those seen with rifampin and pyrazinamide. They may include:
An active tuberculosis (TB) infection is never treated with isoniazid alone. If you have an active TB infection you will need to take several drugs together in addition to isoniazid.
These typically include rifampin, pyrazinamide, and ethambutol. Talk with your doctor or pharmacist to learn more about taking these drugs together and what side effects you can expect.
Does isoniazid cause long-term side effects?
Yes, in some cases, isoniazid oral tablet may cause long-term side effects. These can occur if you take the drug for a long time, or they may last for a while after you’ve stopped taking the drug.
Examples of long-term side effects reported with isoniazid oral tablet include:
Talk with your doctor to learn more about these side effects and how to manage them. Ask your doctor for more information about how long these side effects of isoniazid may last.
* To learn more about this side effect, see the “Side effects of isoniazid in detail” section below.
† Isoniazid oral tablet has a boxed warning for this side effect. A boxed warning is the most serious warning from the FDA.
Side effects of isoniazid in detail
Below you’ll find details on some of the side effects of isoniazid oral tablet.
Hepatitis
Isoniazid oral tablet has a boxed warning for hepatitis. A boxed warning is the most serious warning from the FDA.
In studies, hepatitis was rare in people taking isoniazid oral tablet. This side effect may be serious and even life threatening.
Mild and moderate liver problems are frequent side effects of isoniazid oral tablet. But serious liver damage, including severe and sometimes life threatening hepatitis, has also been reported in rare cases.
Symptoms of hepatitis may include:
- dark urine
- fatigue (low energy)
- general feeling of not being well
- loss of appetite
- nausea or vomiting
- weakness
- yellowing of the skin or whites of the eyes
Certain factors can increase the risk of liver damage with isoniazid oral tablet. These include:
- being age 35 years or older
- alcohol consumption
- chronic liver disease
- injection drug use
Hepatitis can occur at any time during treatment, even after taking isoniazid oral tablet for a long time.
Ways to manage
Your doctor will check your liver function tests from time to time during isoniazid treatment. To help prevent liver problems, you should not drink alcohol while taking isoniazid oral tablet. If you experience symptoms of liver problems, tell your doctor. They can determine whether you should continue taking the drug.
Peripheral neuropathy
Peripheral neuropathy was common in studies of people taking isoniazid oral tablet. This side effect is usually mild but may be serious.
With peripheral neuropathy, you have damage to nerves of the body outside of the brain and spinal cord. Most often, it affects nerves in the arms or legs. Symptoms usually happen in the hands or feet and may include:
- numbness
- pain
- pins-and-needles sensation
- tingling
Peripheral neuropathy with isoniazid is dose-related. This means it’s more common with higher doses of the drug.
Certain factors can increase your risk of peripheral neuropathy with isoniazid oral tablet. These include having diabetes or alcohol use disorder. People who don’t get enough nutrition also have a higher risk.
Ways to manage
If you experience symptoms of peripheral neuropathy, tell your doctor. They can determine the most likely cause and suggest ways to manage it.
Allergic reaction
For some people, isoniazid oral tablet can cause an allergic reaction.
Symptoms can be mild or serious and may include:
- itchiness
- skin rash
- severe skin rashes that may blister and peel
- swelling under the skin, typically affecting eyelids, lips, hands, or feet
- swelling of the mouth, tongue, or throat, which can make it hard to breathe
- flushing (temporary warmth, redness, or deepening of skin color)
Ways to manage
For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.
For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to isoniazid oral tablet, your doctor may recommend taking a different medication instead.
Warnings for isoniazid
Below are some factors you may want to discuss with your doctor before taking isoniazid oral tablet.
Boxed warning: Risk of hepatitis
Isoniazid oral tablet has a boxed warning for the risk of hepatitis. A boxed warning is the most serious warning from the FDA. For details, see the “Side effects of isoniazid in detail” section above.
Other warnings
It may not be safe for you to take isoniazid oral tablet if you have specific health conditions. These are sometimes called drug-condition interactions. Other things may also affect whether isoniazid oral tablet is a safe treatment option for you.
Before taking isoniazid oral tablet, tell your doctor about your health and medications you take. Things to consider include:
Isoniazid and pregnancy
It’s not known whether isoniazid oral tablet should be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.
Isoniazid and breastfeeding
In general, isoniazid oral tablet is considered safe to take while breastfeeding. That said, check with your doctor about whether they feel it’s safe for you specifically.
Isoniazid oral tablet is known to interact with alcohol.
Drinking alcohol while taking isoniazid oral tablet increases the risk of developing liver problems, including hepatitis. Hepatitis with isoniazid treatment can be life threatening.
If you drink alcohol, talk with your doctor about whether it’s safe to consume it during your treatment with isoniazid oral tablet.
What to ask your doctor
This article describes common and serious side effects of isoniazid oral tablet. If your doctor prescribes this medication, they can discuss possible side effects with you. Let your doctor know if you have concerns or questions about treatment with this medication.
Here’s a list of some possible questions you may want to ask your doctor:
- Do I have a higher risk of side effects than other people?
- Can isoniazid oral tablet discolor body fluids, such as urine?
- Does my risk of liver problems depend on the dosage I take?
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
