Pros & Cons of Taking Isoniazid for Tuberculosis (TB)

Tuberculosis (TB) is a contagious infectious disease that mainly affects the lungs but can also affect other body parts such as the spine, brain, and kidneys. When the lungs are affected, the condition is called pulmonary tuberculosis. Some people who become infected by the TB bacteria do not become sick because their immune systems are able to fight this bacteria. This is called a latent TB infection. Others develop TB disease, which can be fatal if it is not treated. Isoniazid is one of the medications used to prevent and treat tuberculosis. Please continue reading to learn about the advantages and disadvantages of taking isoniazid for the treatment of tuberculosis.

What is isoniazid drug used for? How does it work?

Isoniazid is an antibiotic. It works by killing Mycobacterium tuberculosis, the bacteria which cause TB. Isoniazid is used, along with other medications, to treat active tuberculosis infections as well as latent tuberculosis.

Isoniazid is also used to prevent tuberculosis in people with a positive tuberculin skin test, those who are at risk of developing TB due to contact with TB patients, those with pulmonary fibrosis (scarring in the lungs), and those with HIV infection (human immunodeficiency virus).

Similar to other antibiotics, isoniazid can only treat infectious diseases caused by bacteria. They are not effective against viral infections.

What are the advantages of taking isoniazid?

Isoniazid is the first choice antibiotic used for the prevention and treatment of tuberculosis, for both active TB and latent TB.
For the treatment of TB infection, you only need to take isoniazid as a single daily dose or, alternately, 2 or 3 times weekly.
This medication is affordable and is available in a lower-cost generic form.
It comes in tablet form as well as oral liquid or injection forms for people who have difficulty swallowing oral isoniazid tablets.
Isoniazid preventive therapy is available as an option consisting of only isoniazid for TB prevention.

What are the disadvantages of isoniazid?

You need to take isoniazid for several months for complete treatment of tuberculosis.
Isoniazid can have interactions with many other drugs.
This medication may not be suitable for people with certain medical conditions, such as diabetes, peripheral neuropathy (numbness and tingling in the fingers or toes), kidney disease, or HIV.
Isoniazid can cause serious liver problems. The risk is higher in people with active liver disease. Drinking alcohol while on isoniazid can increase the risk of liver damage.
You need to avoid certain foods while on isoniazid, such as certain cheeses, fishes, and certain wines, especially wines with a high content of tyramine or histamine.

What is a major adverse effect of isoniazid?

Common adverse effects of isoniazid include nausea, vomiting, and upset stomach, liver injury, and nerve damage, causing tingling or burning pain in your hands or feet. Tell your doctor if these side effects are severe or do not go away in a few days once your body has had a chance to get used to isoniazid.

More severe isoniazid side effects include:

Severe allergic reaction: skin rash, trouble breathing, swelling of the face, lips, or throat
Severe skin reaction: sore throat, fever, skin rash, skin pain that is reddish or purplish that spreads and causes skin blistering or peeling;
Serious drug reaction affecting many body parts: skin rash, swollen glands, fever, muscle aches, sudden weakness, severe weakness, flu-like symptoms, muscle aches, joint pain, unusual bleeding or bruising such as bleeding gums that won’t stop, or jaundice (yellowing of the skin or the eyes);

Call your doctor immediately if you experience the following adverse effects:

Eye pain, vision changes, or blurred vision
Persistent upper stomach pain that may spread to the back
Dark urine, jaundice, light-colored stools
Sudden weakness, severe dizziness, feeling ill for 3 days or more
Confusion, unusual behavior, trouble remembering or thinking
Convulsions
Unusual bruising or bleeding, such as nosebleeds or bleeding gums

Call your doctor immediately if you develop any of these signs and symptoms or if you develop a serious drug reaction affecting many body parts.

How long is treatment for TB?

Treatment for latent TB infection:

6 or 9 months of isoniazid alone
3 months of once-weekly isoniazid plus rifapentine
3 months of daily isoniazid plus rifampin
4 months of daily rifampin

According to the Center for Disease Control and Prevention, short-course rifamycin-based treatment regimens (3 to 4 months) are preferred over longer courses of isoniazid monotherapy (6 to 9 months) for the treatment of latent TB infection.

Treatment for TB disease:

Drug susceptibility testing is carried out after isolating the TB bacteria from a clinical specimen. This helps doctors identify which medications will work against the bacteria and which medications will be ineffective due to drug resistance. Drug susceptibility testing can take time to complete, but it is important to prevent drug-resistant tuberculosis. Regimens used for treating active TB include:

The 4-month rifapentine-moxifloxacin regimen is recommended for treating pulmonary TB caused by bacteria that are not known or suspected to be drug-resistant. This regimen can be used for the following populations:

Patients 12 years of age and older
Those who weigh 40 kilograms (kg) or more and who have pulmonary tuberculosis
People with HIV with CD4 counts at or above 100 cells/microliter who are receiving or planning to start efavirenz as part of their antiretroviral therapy (ART)
People with a negative sputum culture 6- or 9-months of RIPE treatment of tuberculosis (rifampin, isoniazid, pyrazinamide, ethambutol). RIPE regimens consist of an intensive phase of 2 months, followed by a continuation phase of 4 or 7 months for a total of 6 to 9 months of treatment.

What is the isoniazid dose for active TB?

Isoniazid comes in the form of tablets (50 mg, 100 mg, 300 mg), an oral solution (50 mg/5 mL), and an injection solution (100 mg/mL). The usual dose is as follows:

Adults

Daily regimen: 5 mg/kg (maximum 300 mg) daily in a single dose

15 mg/kg (maximum 900 mg daily) 2 or 3 times per week

Children

Daily regimen: 10-15 mg/kg (maximum 300 mg) daily as a single dose

20-40 mg/kg (maximum 900 mg daily) 2 or 3 times per week

Pyridoxine (vitamin B6) at doses of 25-50 mg per day is prescribed to patients taking isoniazid who are at an increased risk of peripheral neuropathy (nerve problems), including pregnant women, breast feeding infants being nursed on breast milk, elderly individuals, and people with malnutrition, alcoholism, diabetes, chronic renal failure, or HIV infection. Patients who already have peripheral neuropathy are recommended a total of 100 mg of pyridoxine per day.

Inform your doctor if you have the following conditions

Isoniazid should be avoided in the following individuals:

Those with a hypersensitivity (allergic) reaction to isoniazid.
Those with a history of isoniazid-induced hepatitis (liver damage).
Those with active liver disease
Those who had severe isoniazid side effects in the past, such as fever, chills, or joint pain

Isoniazid should be used with caution for people with the following risk factors:

People who drink alcohol daily (it is recommended you avoid drinking alcohol as alcohol can increase the risk of isoniazid-induced liver injury)
Patients with active liver disease or severe renal dysfunction (kidney disease)
Pregnant women
Serious liver injury can be at higher risk in women, especially those who have recently given birth, or women of Hispanic or African-American ancestry
People with peripheral neuropathy (nerve problems) or medical conditions that predispose them to neuropathy.
People who use any injectable drugs.
People with HIV infection or AIDS.

How safe is isoniazid?

Isoniazid is generally safe when used as directed. It’s important that you read the prescription label carefully and take the medicine exactly as directed. Like with most medications, isoniazid can cause side effects and carries certain risks. You should take the following precautions during isoniazid treatment of tuberculosis to lower your risk of serious complications.

Drug interactions

Give your healthcare professional a list of all your medicines, including prescription drugs, over-the-counter medications, dietary supplements, and herbal products. This will help avoid potentially dangerous drug interactions.

Laboratory tests

Your doctor will order certain lab tests prior to starting treatment and monthly or more frequently during isoniazid treatment. This is to keep an eye on your liver function by measuring liver enzymes. Keep all laboratory lab and medical appointments during isoniazid therapy. If you develop signs of liver damage, such as abnormal liver function tests, fatigue, loss of appetite, upper stomach pain, nausea, or jaundice (yellowing of the skin or eyes), you may need to discontinue drug therapy with isoniazid.

Directly observed therapy

Your healthcare professional may recommend directly observed therapy for tuberculosis. This means you will meet with a healthcare worker to take the TB medication. Directly observed therapy lowers the risk of treatment failure and drug-resistant TB due to incomplete treatment or not taking the medication at the prescribed frequency. It also helps you complete tuberculosis treatment quickly without gaps and prevents the spread of TB to others.

Missed dose

Avoid skipping doses. If you miss a dose of isoniazid, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose or extra medicine to make up for a missed dose. Setting an alarm or reminder on your phone can be helpful to remind you to take the medication.

Overdose

In case of an overdose, call your doctor immediately or contact your local poison control center or the national poison control center at 1-800-222-1222, or go to the nearest emergency room. Isoniazid overdose symptoms may include nausea, vomiting, severe dizziness, vision problems, increased urination, hallucinations, slurred speech, or loss of consciousness.

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