Organ transplantation has saved the lives of millions of patients around the world. However, even with substantial advancements in medicine, organ recipients still face significant health risks and complications as a result of the transplantation surgery and the medications they must take afterward.

Recipients of kidney transplants need to take anti-rejection drugs to prevent the body rejecting the organ, but these drugs weaken the immune system and can leave the patients at risk of infection. People who are taking anti-rejection medications following a kidney transplant are up to 300 times more likely to contract tuberculosis (TB) than the average person. This increased risk can be extremely dangerous in regions where TB is a common infection, such as India and Pakistan.

A new study analyzed the results of three studies carried out in India and Pakistan that tracked 558 patients who received kidney transplants in these countries. The researchers found that patients who were given a drug known as isoniazid, which is used to treat TB, were much less likely to develop the disease in the year following the transplant surgery.

Isoniazid is a medication that interferes with bacterial enzymes in the body to fight the TB infection. It kills mycobacteria, including the family of mycobacterial strains that can cause tuberculosis, but only when they are dividing.

As a result, isoniazid must be taken for several months to eliminate the TB-causing bacteria from the body. However, it can be effective at preventing TB in at-risk patients who are exposed to the infection, such as transplant recipients who live in areas with a high prevalence of TB.

All three studies found that patients who were given isoniazid in addition to anti-rejection medication following a kidney transplant developed TB at much lower rates than patients who received no anti-tuberculosis medication.

One issue with the use of isoniazid is that it is known to increase the risk of liver disease. According to the recently-published review, the patients most likely to suffer liver damage as a result of taking isoniazid were those who already had a history of liver disease. The patients at highest risk were those who had liver damage caused by a hepatitis B or hepatitis C infection.

Although there is a clear benefit of taking isoniazid after kidney transplantation to reduce the risk of contracting TB, the overall benefit is not so evident for patients who already have liver damage, as the anti-TB medication could cause further harm to the liver. The benefits are also not so obvious in regions where the prevalence of TB is low.

Future research is needed to determine what the balance is between the benefits and the risks of giving anti-TB medications to patients who have undergone a kidney transplant.

Understanding the risks faced by certain groups of patients taking immune-suppressing anti-rejection drugs is crucial to giving each patient the best possible treatment. Physicians must weigh the risks of the patient rejecting the organ — which could lead to death if another organ donor cannot be found — against the risks of infection.

In addition, the long-term risks and benefits of using drugs to control infection must be considered, taking into account the patient's risk of exposure to pathogens and underlying health issues.