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Isoniazid Preventive Therapy

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Isoniazid preventive therapy (IPT) reduces the risk of the first episode of tuberculosis. Continue reading to know more.

Medically reviewed by

Dr. Kaushal Bhavsar

Published At May 17, 2023
Reviewed AtOctober 11, 2023


Tuberculosis is the most common opportunistic infection, especially among HIV-infected persons. In HIV patients, it is the primary cause of mortality, and they possess the risk throughout. Isoniazid preventive therapy is the administration of INH (Isoniazid) to people with latent tuberculosis infection to prevent its progression to active tuberculosis disease.

What Is Isoniazid Preventive Therapy?

Preventive therapy is also known as chemoprophylaxis. Isoniazid is one of the most efficient bactericidal and anti-tuberculosis drugs. This drug protects against the progression of tuberculosis (TB) infection to active disease and the recurrence of the tuberculosis infection after exposure to any open case of TB. It has been proved that Isoniazid preventive therapy is very effective and safer than Pyrazinamide and Rifampicin regimens used to prevent latent TB infection. It was also found that Isoniazid preventive therapy effectively reduced the incidences of tuberculosis and death in HIV-infected patients. Isoniazid preventive therapy is used to prevent active TB infection, reinfection, and relapse, and the toxicity is as good as a regimen that includes Rifampicin, Pyrazinamide, and Rifapentine. Isoniazid preventive therapy reduces the overall risk of developing tuberculosis by 33 percent. Isoniazid preventive therapy should be avoided if monthly monitoring is not possible. The patients should be educated and should be monitored monthly in person.

How Is Isoniazid Therapy Given in Children?

Children with TB infection differ from adults in their response to the disease. As the children are at risk of progression of TB disease, they are targeted for preventive treatment. Children more commonly develop TB infections as compared to adults. So, there is a need for improvement in the diagnosis, prevention, and treatment of TB infection in children by including NTPs in line with proper standards and guidelines. The NTPs successfully and effectively prevent TB in children. If the children are diagnosed with active TB, then an entire course of anti-TB treatment is given to them. If the children do not have active TB, Isoniazid (INH) should be given 4.53 mg/lb daily for six months. The main groups for preventive therapy include the individuals who are the most at risk of acquiring TB are:

  • PLHIV (people living with HIV).

  • Infants and children in contact with TB patients.

How Is Isoniazid Preventive Therapy Given to Pregnant Women?

The efficacy, safety, and appropriate timing of Isoniazid therapy for tuberculosis prevention in pregnant women with HIV infection receiving antiretroviral treatment are unknown. A trial conducted included a multicenter, placebo-controlled, double-blind trial for pregnant women with HIV infection to receive Isoniazid preventive therapy for 28 weeks, initiated during pregnancy or at 12 weeks after the delivery. The infants and the mothers were followed through 48 weeks after the delivery. The World Health Organization (WHO) recommends that the treatment for active TB has not yet developed preventive therapy during pregnancy. In addition, clinical and laboratory monitoring has shown reports of Isoniazid-related hepatotoxicity in pregnant and postpartum women. Some studies have shown that Hispanic and black women, especially postpartum, may be at higher risk of severe or fatal reactions, so they should be monitored closely.

How Is Isoniazid Preventive Therapy Given in HIV Patients?

The risk for people with both M. tuberculosis and HIV is much higher than those without HIV infection. However, the people with latent TB who took Isoniazid benefit have shown a significant reduction in the infection, observed in HIV-negative and HIV-positive, and TST (tuberculin skin test)-positive individuals. In addition, there is a reduction in the risk of developing active TB, around 60 percent in HIV and TST-positive individuals with a high prevalence of TB. Therefore, the world health organization recommends that information about Isoniazid preventive therapy be made available to all PLHIV, and Isoniazid preventive therapy itself should be offered as a care package to all HIV-infected. TST-positive individuals, those individuals with active TB have been safely excluded.

In conditions where a TST test cannot be performed or carried out, HIV patients, when treated with Isoniazid, reduce the risk of developing active TB by 40 percent. In the conditions where TST testing is not available, then the individuals should be considered for preventive therapy if they are infected with HIV:

  • Health care workers.

  • Prisoners.

  • Miners.

  • People with a high risk of transmitting or acquiring TB infection.

  • In-house contacts with TB patients.

  • Individuals are living in areas where M. tuberculosis infection is prevalent.

What Are the Benefits of Isoniazid Preventive Therapy?

Appropriately and adequately Isoniazid preventive therapy plays a vital role in eliminating tuberculosis. In the area with a high prevalence of TB, the duration of Isoniazid preventive therapy should be six months for full benefit. The primary purpose of Isoniazid preventive therapy is to prevent latent infection from developing into a clinical disease and is also used in the prevention of initial infection and prevention of recurrence of past infection.

What Are the Adverse Effects of Isoniazid Preventive Therapy?

The adverse effects of Isoniazid preventive therapy for latent TB infection include:

  • Gastrointestinal and Hepatic Effects - The adverse effects were gastrointestinal symptoms, including hepatotoxicity and hepatitis.

  • Dermatological Effects - Few patients developed generalized rashes and acneiform rashes. No patients reported alopecia.

  • Neuropsychiatric Effects - Most common neuropsychiatric effects reported were lethargy and cognitive impairment. Few people reported headaches, disturbance in sleep, and blurred vision.


Preventive therapy has mainly been used for its beneficial effects on the individual. Therefore, preventive therapy is recommended for HIV-positive people who do not have active TB infection. The patients should be thoroughly educated and monitored monthly, in person, by appropriately trained personnel.

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Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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