Рифабутин

Описание

Rifabutin, a rifamycin antibacterial derivative, is the first agent approved and introduced for the prevention of Mycobacterium avium complex (MAC) in AIDS patients. It is also indicated in combination chemotherapy for the prophylaxis and treatment of MAC infections in HIV positive patients and for newly diagnosed and chronic tuberculosis.

Химические свойства

Red-Brown Powder

Использование

Rifamycins are antibiotics that inhibit DNA-dependent RNA polymerases and are usually bactericidal against Gram-positive bacteria but bacteriostatic against Gram-negative bacteria. Rifamycins are also effective against Mycobacterium species, including M. tuberculosis. Rifabutin is a broad-spectrum rifamycin antibiotic that has applications against tuberculosis, H. pylori, M. avium complex, Chlamydia, and other bacteria. It is also useful in co-infections with human immunodeficiency virus, including tuberculosis.

Показания

Rifabutin (Mycobutin), an antibiotic related to rifampin, shares its mechanism of action, that is, inhibition of RNA polymerase. Rifabutin has significant activity in vitro and in vivo against M. avium-intracellular complex (MAC) isolates from both HIV-infected and non–HIV-infected individuals. It has better activity against MAC organisms than rifampin. Rifabutin is active against M. tuberculosis, including some rifampinresistant strains, such as M.leprae and M.fortuitum. It has a spectrum of activity against gram-positive and gramnegative organisms similar to that of rifampin. The molecular basis for resistance to rifabutin is shared by both rifampin and rifabutin; this explains the virtually complete cross-resistance that occurs between these drugs.

Антимикробная активность

The activity is similar to that of rifampicin, but it is more active against the Mycobacterium avium complex (MIC 0.01–2 mg/L) and several other atypical mycobacteria. It inhibits the replication of human immunodeficiency virus 1 (HIV-1) in concentrations (10 mg/L) that are not toxic to lymphoid cells, but no efficacy on HIV infections has been demonstrated.

Приобретенная устойчивость

The frequency of spontaneously resistant mutants in several bacterial species, including M. tuberculosis, M. leprae, Staphylococcus aureus and Chlamydia trachomatis, is somewhat lower than with rifampicin.

Фармацевтические приложения

Rifabutine; ansamycin. Molecular weight: 847.02.
A semisynthetic spiropiperidyl derivative of rifamycin S, available for oral administration. It is slightly soluble in water and soluble in organic solvents.

Фармаколо?гия

Rifabutin is well absorbed orally, and peak plasma concentrations are reached in 2 to 3 hours. Because of its lipophilicity, rifabutin achieves a 5- to 10-fold higher concentration in tissues than in plasma. The drug has a half-life range of 16 to 96 hours and is eliminated in urine and bile.
Rifabutin appears as effective as rifampin in the treatment of drug-susceptible tuberculosis and is used in the treatment of latent tuberculosis infection either alone or in combination with pyrazinamide. Clinical use of rifabutin has increased in recent years, especially in the treatment of HIV infection. It is a less potent inducer of cytochrome 450 enzymes pathways than rifampin and results in less drug interaction with the protease inhibitors and nonnucleoside reverse transcriptase inhibitors. Rifabutin is therefore commonly substituted for rifampin in the treatment of tuberculosis in HIV-infected patients. Another important use of rifabutin in the HIV-infected population is prevention and treatment of disseminated MAC.

Фармакокине?тика

Oral absorption：12–20%
C_max 300 mg oral ：0.38 mg/L after 3.3 h
Plasma half-life：16 h
Volume of distribution：9.3 L/kg
Plasma protein binding： 85%
absorption and distribution
Oral absorption is rapid but incomplete, with considerable interpatient variation. It is well distributed, concentrations in many organs being higher than that in plasma. The average concentration in lungs is 6.5 times the simultaneous plasma concentration.
Metabolism and excretion
Rifabutin is mainly metabolized to the active desacetyl derivative, although several other oxidation products have been detected in urine, where some 10% of the dose is eliminated. About 30–50% of the dose can be recovered from the feces. Elimination from plasma is biphasic, with a terminal half-life of 45 h. The drug is a weak inducer of hepatic enzymes. The rate of metabolism increases, and the plasma area under the concentration–time curve (AUC) declines as the treatment continues.

Клиническое использование

Prevention of infections with M. avium complex in AIDS patients
Treatment of non-tuberculous mycobacterial disease (in combination with other agents)
Rifabutin in combination with other agents has been proposed as a rescue therapy after Helicobacter pylori treatment failures.Although some efficacy has been observed in the treatment of tuberculosis, its use for this condition is not recommended.

Побочные эффекты

The adverse effects that most frequently result in discontinuation of rifabutin include GI intolerance, rash, and neutropenia. Rifabutin levels will be increased with concurrent administration of fluconazole and clarithromycin, resulting in anterior uveitis, polymyalgia syndrome, and a yellowish-tan discoloration of the skin (pseudojaundice). Other adverse reactions are similar to those of rifampin, such as hepatitis, red-orange discoloration of body fluids, and drug interactions due to effects on the hepatic P450 cytochrome enzyme system.