Elena S. Hollender

Pharmacokinetic Evaluation of Rifabutin in Combination with Lopinavir-Ritonavir in Patients with HIV Infection and Active Tuberculosis

BACKGROUND Human immunodeficiency virus (HIV)-associated tuberculosis is difficult to treat, given the propensity for drug interactions between the rifamycins and the antiretroviral drugs. We examined the pharmacokinetics of rifabutin before and after the addition of lopinavir-ritonavir. METHODS We analyzed 10 patients with HIV infection and active tuberculosis in a state tuberculosis hospital. Plasma was collected for measurement of rifabutin, the microbiologically active 25-desacetyl-rifabutin, and lopinavir by validated high-performance liquid chromatography assays. Samples were collected 2-4 weeks after starting rifabutin at 300 mg thrice weekly without lopinavir-ritonavir, 2 weeks after the addition of lopinavir-ritonavir at 400 and 100 mg, respectively, twice daily to rifabutin at 150 mg thrice weekly, and (if rifabutin plasma concentrations were below the normal range) 2 weeks after an increase in rifabutin to 300 mg thrice weekly with lopinavir-ritonavir. Noncompartmental and population pharmacokinetic analyses (2-compartment open model) were performed. RESULTS Rifabutin at 300 mg without lopinavir-ritonavir produced a low maximum plasma concentration (C(max)) in 5 of 10 patients. After the addition of lopinavir-ritonavir to rifabutin at 150 mg, 9 of 10 had low C(max) values. Eight patients had dose increases to 300 mg of rifabutin with lopinavir-ritonavir. Most free rifabutin (unbound to plasma protein) C(max) values were below the tuberculosis minimal inhibitory concentration. For most patients, values for the area under the plasma concentration-time curve were as low or lower than those associated with treatment failure or relapse and with acquired rifamycin resistance in Tuberculosis Trials Consortium/US Public Health Service Study 23. One of the 10 patients experienced relapse with acquired rifamycin resistance. CONCLUSION The recommended rifabutin doses for use with lopinavir-ritonavir may be inadequate in many patients. Monitoring of plasma concentrations is recommended.

Use of Rifabutin with Protease Inhibitors for Human Immunodeficiency Virus-Infected Patients with Tuberculosis

Drug interactions between rifamycins and highly active antiretroviral therapy (HAART) have raised concerns in the treatment of human immunodeficiency virus (HIV)-infected patients with tuberculosis. We conducted a study of this interaction by measuring serum drug levels of all HIV-infected patients with tuberculosis who were admitted to A. G. Holley State Tuberculosis Hospital (Florida) from October 1997 through December 1998, who were concomitantly treated with rifabutin and HAART. All 25 patients studied became culture-negative within 2 months of initiation of therapy for tuberculosis and remained negative for a median of 13 months follow-up after completion of therapy. HIV viral loads (mean+/-SEM) decreased significantly from 4.95+/-0.21 log10 copies/mL before initiation of HAART to 2.77+/-0.07 log10 copies/mL before discharge (P<.001); 20 of 25 patients achieved viral loads of <500copies/mL. In summary, the concomitant use of rifabutin and HAART can lead to successful treatment of HIV-infected patients with tuberculosis without increased side effects.

Feasibility of Shortening Respiratory Isolation with a Single Sputum Nucleic Acid Amplification Test

RATIONALE Serial smear analysis to guide respiratory isolation (RI) of patients with suspected tuberculosis (TB), the majority of whom will be found not to have TB, leads to expensive and unnecessary isolation, and may potentially result in decreased vigilance of subjects with respiratory compromise. OBJECTIVES To compare the performance of a single first-sputum, Mycobacterium tuberculosis-specific nucleic acid amplification (NAA) test with three sputum smears for assessing the need for RI. METHODS Prospective evaluation of 493 patients with suspected TB (74% HIV positive) admitted to RI in a major county hospital in the United States, who had at least three sputum smears and material available from the first sample for additional NAA testing. MEASUREMENTS AND MAIN RESULTS Accuracy of the first sputum NAA result and serial smears for identifying patients with potentially infectious TB who truly require RI was determined. Forty-six patients (9.3%) had TB confirmed by culture. First-sputum NAA test detected all patients with TB who had a positive smear (n = 35), even when the first of the three specimens was smear negative. In addition, when compared with serial smears, the first-sputum NAA had a higher sensitivity (0.87; 95% confidence interval [CI], 0.74-0.95) and specificity (1.0) in the detection of subjects with positive M. tuberculosis cultures (smear sensitivity, 0.76; 95% CI, 0.61-0.87; and specificity, 0.96; 95% CI, 0.94-0.98). CONCLUSIONS A single first-sputum NAA testing can rapidly and accurately identify the subset of patients with suspected TB who require RI according to serial sputum smears. Its potential use to shorten RI time does not preclude the need to obtain subsequent specimens for culture.

Ofloxacin population pharmacokinetics in patients with tuberculosis.

SETTING Two tuberculosis hospitals in the United States. OBJECTIVE To determine the population pharmacokinetic (PK) parameters of ofloxacin following multiple oral doses. DESIGN A total of 73 patients with tuberculosis (TB) participated in the study. Subjects received multiple doses of ofloxacin as part of their treatment. They also received concurrent medications based on in vitro susceptibility data. Serum samples were collected over 10 h and assayed by a validated high performance liquid chromatography (HPLC) assay. Concentration-time data were analyzed using population methods. RESULTS Ofloxacin concentrations increased linearly with increasing oral doses. Delayed absorption was seen at least once in 29% of patients. Ofloxacin elimination decreased with declining renal function and increasing age. Higher daily doses were well tolerated, and appeared to maximize the peak concentration to minimal inhibitory concentration ratio (Cmax:MIC). CONCLUSION Ofloxacin PK parameters were comparable to those previously published for other patient populations. Higher daily doses may offer pharmacodynamic advantages for the treatment of TB.

Chapter 17 – Mycobacterial Disease in Patients with HIV Infection

This chapter reviews the important aspects of the interplay of HIV infection with mycobacteria, particularly focusing on features that are clinically relevant. HIV infection has been one of the principal reasons for the recent increase in incidence of mycobacterial diseases worldwide. Understanding TB in patients infected with HIV is important from many standpoints. First, among tuberculosis-infected individuals, immunosuppression because of HIV is the greatest known single risk factor for progression to TB disease. Second, TB differs from other HIV-related infections in that it is spread respiratorily from person to person both in normal and immunocompromised hosts. There is, therefore, significant potential for an aerosol-transmitted disease such as TB to spread rapidly among HIV-infected persons exposed to each other and from them to non-HIV infected contacts. Finally, mycobacterial disease in HIV-infected patients often presents with an atypical clinical picture: tuberculin skin anergy is common, the chest radiograph is often atypical, and there is a high incidence of extrapulmonary and disseminated disease, all contributing to confound the diagnosis, which may easily be missed unless these features are appreciated.