Rifabutin is counted among the tuberculostatics. These are special antibiotics for the therapy of tuberculosis.
What is rifabutin?
Rifabutin is counted among the tuberculostatics. These are special antibiotics for the therapy tuberculosis. Rifabutin is an antibiotic belonging to the group of antibiotic bactericides. It is sold under the trade name Mycobutin and is a semisynthetic rifamycin derivative. This is suitable for the treatment of mycobacteria as well as gram-positive and gram-negative infections. Rifabutin belongs to the group of tuberculostatics. This means that the drug is used specifically for the treatment of tuberculosis. As a rule, tuberculosis treatment is carried out in combination with other tuberculostatics such as rifampicin, isoniazid, ethambutol or pyrazinamide in order to counteract the development of resistance. Rifabutin was approved in Europe in the mid-1990s. Since 2011, the active ingredient has been on the WHO (World Health Organization) list of essential medicines.
Pharmacologic action
The mode of action of rifabutin is similar to that of rifampicin. Thus, rifabutin also inhibits the DNA-dependent RNA polymerase of susceptible bacteria, resulting in a blockade of protein synthesis by the germs. Furthermore, there are indications that the DNA synthesis of the bacteria is also affected. To some extent, rifabutin can also exert its positive effect against Mycobacterium tuberculosis strains that are resistant to rifampicin. In contrast to rifampicin, the activity of rifabutin is much higher due to the inhibition of RNA polymerase. While around 94 percent of all mycobacteria are already resistant to rifampicin, only around 20 percent are resistant to rifabutin, which is another advantage of the tuberculostat. In addition, rifabutin has biological activity against the bacterial genus Heliobacter. When rifabutin is taken by mouth, its effect is enhanced by the simultaneous ingestion of protein-containing foods. The antibiotic is partially metabolized by the liver. Up to 85 percent of rifabutin binds to protein (egg white). Rifabutin reaches its highest level in the organism’s blood plasma after a period of about six to eight hours. Most of the active substance leaves the body via the kidneys. The half-life of the tuberculostat varies between 28 and 62 hours.
Medical use and application
For use, rifabutin is used to prevent Mycobacterium avium-intracellulare (MAI) infection in patients with AIDS. Treatment is also available for MAI infection. This is done in combination with other antibiotics such as ethambutol, azithromycin and clarithromycin. In addition, medicine resorts to rifabutin to treat multidrug-resistant tuberculosis. Furthermore, rifabutin is effective against bacterial pathogens such as Mycobacterium paratuberculosis, Mycobacterium leprae and Chlamydia pneumoniae. Furthermore, therapy of the chronic inflammatory bowel disease Crohn’s disease is also possible. The usual dose for taking rifabutin is 450 to 600 milligrams of rifabutin per day. However, if clarithromycin is administered concomitantly, the daily dose is reduced to 300 milligrams. The duration of treatment is usually six months. For prophylaxis of MAC (Mycobacterium avium complex) infections in AIDS patients, the usual daily dose is 300 milligrams. To prevent the development of resistance, it is advisable to rule out infections with mycobacteria in advance. If patients have previously received other tuberculostatics, an increase in the dose to 300 to 450 milligrams is recommended. Increasing the dose is particularly useful in patients who are immunosuppressed. Rifabutin can be taken at any time of day and independently of meals. In this case, the capsule is taken once a day.
Risks and side effects
When using rifabutin, the occurrence of undesirable side effects is possible. They are similar to the side effects of taking rifampicin. Thus, there is often an increase in liver enzymes, nausea and vomiting.Other conceivable side effects may include skin rash, pain in the upper abdomen, diarrhea, chest pain, changes in the sense of taste, migraine-like headache, sore throat, flu-like symptoms, bruising, anxiety, or jaundice. Sometimes stool, urine, sweat, tears, and saliva turn orange-brown during rifabutin treatment. Rifabutin should not be taken if the patient is hypersensitive to the active substance. There is a risk of bronchospasm, eosinophilia (special form of leukocytosis) or shock. Combination treatment with clarithromycin also increases the risk of inflammation of the iris (uveitis). A disadvantage of rifabutin is the marked likelihood of interactions with other drugs, such as those used to treat AIDS. Thus, it is possible that the effect of the preparations is weakened. The drugs affected include anticoagulants, analgesics such as opioids, hormonal contraceptives, glucocorticoids, and the active ingredients phenytoin, digitoxin, cotrimoxazole, and dapsone. In turn, the mode of action of rifabutin may be affected by concomitant administration of drugs such as cimetidine, erythromycin, clarithromycin, ketoconazole, and fluconazole.
