Once-Daily Regimen of Saquinavir, Ritonavir, Didanosine, and Lamivudine in HIV-Infected Patients With Standard Tuberculosis Therapy (TBQD Study)

Pharmacokinetics and 48 week efficacy of adjusted dose indinavir/ritonavir in rifampicin-treated HIV/tuberculosis-coinfected patients: a pilot study

HIV/tuberculosis (HIV/TB)-coinfected patients intolerant/resistant to nonnucleoside reverse transcriptase inhibitors (NNRTIs) have limited treatment options. We evaluated the pharmacokinetics (PK)/safety/efficacy of an adjusted dose of indinavir/ritonavir (IDV/r) 600/100 mg plus two NRTIs in HIV/TB-coinfected Thais receiving rifampicin-based anti-TB treatment. This was a prospective, open-label study. Eighteen Thai, HIV/TB-coinfected patients between 18 and 60 years were recruited. IDV/r 600 mg/100 mg plus lamivudine and stavudine were administered every 12 h (bid). When rifampicin was stopped, IDV/r was reduced to 400/100 mg BID. Clinical outcomes, adverse events, and concomitant drugs were intensively collected. Intensive 12-h PK was performed after 2 weeks of IDV/r while on rifampicin. Samples were collected: predosing and 1, 2, 3, 4, 6, 8, 10, and 12 h after drug intake. The median body weight was 55 kg. The median CD4 was 26 cells/μl. The median HIV RNA was 5.05 log(10) copies/ml. Then 15/18 underwent intensive PK at week 2. The median time between initiating rifampicin and IDV/r was 4.5 months. The median duration of rifampicin during study (rifampicin/IDV/r together) was 15.6 weeks. All received a total of 9 months of antituberculous drugs. The geometric means (GM) of indinavir AUC(0-12) and C(12) were 8.11 mg*h/liter and 0.03 mg/liter, respectively. After stopping rifampicin and reducing IDV/r to 400/100 bid, the GM indinavir C(12) increased to 0.68 mg/liter (p=0.004). In all, 8/18 (44%) had asymptomatic ALT elevation and 2/18 (11%) had symptomatic hepatotoxicity requiring IDV/r discontinuation. All 13 patients who remained on IDV/r treatment had HIV RNA <50 copies/ml at 48 weeks. Concomitant use of rifampicin and IDV/r resulted in subtherapeutic indinavir concentrations. Although 44% of them developed asymptomatic Grade 3/4 transaminitis, the rate of study drug discontinuation due to hepatotoxicity was low. Despite good virological outcome in our cohort, prolonged exposure to subtherapeutic indinavir concentrations may lead to treatment failure.

Unexpected Hepatotoxicity of Rifampin and Saquinavir/Ritonavir in Healthy Male Volunteers

OBJECTIVES: Rifampin is a potent inducer of the cytochrome P450 3A4 isoenzyme (CYP3A4) that metabolizes most protease inhibitor (PI) antiretrovirals. This study was designed to evaluate the steady-state pharmacokinetics and tolerability of the coadministration of the PIs saquinavir and ritonavir (a CYP3A4 inhibitor used as a pharmacoenhancer of other PIs) and rifampin when coadministered in healthy HIV-negative volunteers. METHODS: In an open-label, randomized, one sequence, two-period crossover study involving 28 healthy HIV-negative volunteers, arm 1 was randomized to receive saquinavir/ritonavir 1000/100 mg twice daily while arm 2 received rifampin 600 mg once daily for 14 days. Both arms were then to receive concomitant saquinavir/ritonavir and rifampin for 2 additional weeks. Vital signs, electrocardiography, laboratory analyses, and blood levels of total saquinavir, ritonavir, rifampin, and desacetyl-rifampin, the primary metabolite of rifampin, were measured. RESULTS: In arm 1, 10/14 (71%) and, in arm 2, 11/14 (79%) participants completed the first study phase; eight participants in arm 1 and nine in arm 2 went on to receive both saquinavir/ritonavir and rifampin. Following substantial elevations (>/= grade 2) in hepatic transaminases in participants receiving the coadministered agents, the study was discontinued prematurely. Two participants in arm 1 displayed moderate elevations after five and four doses of rifampin, respectively. In arm 2, all participants experienced severe elevations within 4 days of initiating saquinavir/ritonavir. Clinical symptoms (e.g., nausea, vomiting, abdominal pain, and headache) were more common and severe in arm 2. Clinical symptoms abated and transaminases normalized following drug discontinuation. Limited pharmacokinetic data suggest a possible relationship between transaminase elevation and elevated rifampin and desacetyl-rifampin concentrations. CONCLUSIONS: Although not confirmed in HIV-infected patients, the data indicate that rifampin should not be coadministered with saquinavir/ritonavir.

Saquinavir exposure in HIV-infected patients with chronic viral hepatitis

OBJECTIVES

The aim of this study was to assess the influence of hepatitis B virus or hepatitis C virus co-infection and the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics in HIV-infected subjects without liver function impairment.

METHODS

A cross-sectional, comparative study enrolling HIV-infected adults receiving saquinavir/ritonavir 1000/100 mg twice daily or 1500/100 mg once daily was conducted. Patients with chronic viral hepatitis (HEP+) were grouped as having advanced liver fibrosis (HEP+/FIB+) or not (HEP+/FIB-) based on the FIB-4 index. Saquinavir and ritonavir trough concentrations (C(trough)) in plasma were determined by HPLC. The geometric mean ratio (GMR) was used to compare saquinavir and ritonavir C(trough) between HEP- and HEP+ patients, and the influence of the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics was explored using analysis of variance.

RESULTS

One hundred and thirty-eight patients on twice-daily saquinavir/ritonavir (67 HEP-, 71 HEP+) and 36 patients on once-daily saquinavir/ritonavir (12 HEP-, 24 HEP+) were included. Saquinavir C(trough) was comparable between HEP- and HEP+ patients receiving either saquinavir/ritonavir 1000/100 mg twice daily [GMR 0.91, 95% confidence interval (CI) 0.60-1.37; P = 0.655] or 1500/100 mg once daily (GMR 0.88, 95% CI 0.39-1.97; P = 0.752). Similarly, ritonavir C(trough) was also comparable between HEP- and HEP+ patients. The extent of liver fibrosis was not significantly related to saquinavir or ritonavir C(trough) in patients receiving either of the two studied doses.

CONCLUSIONS

Saquinavir C(trough) was not increased in HIV-infected patients with chronic viral hepatitis in the absence of liver function impairment. These results confirm that no specific dose modification of saquinavir/ritonavir should be recommended in this setting.

Update on rifampin and rifabutin drug interactions

Rifampin is a potent inducer of cytochrome P-450 oxidative enzymes as well as the P-glycoprotein transport system. Several examples of well-documented clinically significant interactions include warfarin, oral contraceptives, cyclosporine, itraconazole, digoxin, verapamil, nifedipine, simvastatin, midazolam, and human immunodeficiency virus-related protease inhibitors. Rifabutin reduces serum concentrations of antiretroviral agents, but less so than rifampin. Examples of clinically relevant interactions demonstrated by recent reports include everolimus, atorvastatin, rosiglitazone/pioglitazone, celecoxib, clarithromycin, caspofungin, and lorazepam. To avoid a decreased therapeutic response, therapeutic failure, or toxic reactions when rifampin is added to or discontinued from medication regimens, clinicians need to be cognizant of these interactions. Studies and cases of rifampin drug interactions continue to increase rapidly. This review is a timely reminder to clinicians to be vigilant.

Pathogenesis and management of HIV/TB co-infection in Asia

HIV infection increases the risk of reactivation of latent tuberculosis (TB), progression of a new infection or re-infection to active disease, and acceleration of the natural course of the disease with a more rapid spread of strains, including those that are drug resistant, in the community. TB also accelerates the course of HIV-induced disease by activating viral replication and accentuating the decline in CD4 T cell counts. In this chapter, TB-HIV co-infection is discussed in the context of the situation in Vietnam, particularly Ho Chi Minh City, the creation of a well-integrated TB control and research programs in Cambodia, and the broad principles of the co-management of TB/HIV particularly in the context of the associated atypical forms of pulmonary TB (PTB), increased non-PTB and the frequency of acid fast smear negative cases.

Complications of Antiretroviral Therapy in Patients with Tuberculosis: Drug Interactions, Toxicity, and Immune Reconstitution Inflammatory Syndrome

Access to antiretroviral therapy is rapidly expanding in resource-limited settings, where tuberculosis is the most common opportunistic infection. Coadministration of antitubercular and antiretroviral agents is, therefore, occurring commonly, and it is associated with 3 major complications. First, induction of cytochrome P-450 enzymes and P-glycoprotein by rifampin results in reduced concentrations of nonnucleoside reverse-transcriptase inhibitors and, particularly, protease inhibitors. This potentially results in the loss of antiviral efficacy and the development of viral resistance. Replacing rifampin with rifabutin, which does not significantly affect the concentrations of antiretroviral agents, is advocated but is currently unaffordable in resource-limited settings. Second, overlapping toxicities of antitubercular and antiretroviral agents occur frequently, necessitating discontinuation of therapy and increasing the risk of nonadherence. Third, immunopathological reactions, termed "the immune reconstitution inflammatory syndrome," occur frequently when antiretroviral therapy is initiated in patients with tuberculosis. These complexities of coadministration of antitubercular and antiretroviral agents are reviewed, and research priorities are highlighted.

Pharmacokinetic interaction between rifampicin and the once-daily combination of saquinavir and low-dose ritonavir in HIV-infected patients with tuberculosis

OBJECTIVES

To assess plasma steady-state pharmacokinetics (PK) of rifampicin, isoniazid, saquinavir and ritonavir in HIV and tuberculosis (TB) co-infected patients, and investigate potential interactions between TB drugs and protease inhibitors (PIs).

METHODS

Open-label, single-arm, sequential PK study including 22 patients with HIV infection and TB. During the first 2 months, patients received rifampicin, isoniazid and pyrazinamide, with or without ethambutol (first PK study, n = 22). Then patients stopped pyrazinamide and ethambutol and started once-daily antiretroviral therapy (ART) with didanosine, lamivudine, ritonavir (200 mg) and saquinavir (1600 mg) (second PK study, n = 18). Patients stopped all TB drugs after 9 months continuing the same ART (third PK study, n = 15). Differences between TB drug parameters in the first and second PK studies, and between PI parameters in the second and third PK studies were used to assess interactions.

RESULTS

Rifampicin and isoniazid pharmacokinetics did not change substantially with saquinavir and ritonavir. A significant 39.5%, 34.9% and 48.7% reduction in median saquinavir AUC(0-24), C(max) and C(trough), respectively, was seen with rifampicin and isoniazid. Ritonavir AUC(0-24), C(max) and C(trough) decreased 42.5%, 49.6% and 64.3%, respectively, with rifampicin and isoniazid.

CONCLUSIONS

There was a significant interaction between saquinavir, ritonavir and rifampicin, with reduction in median plasma concentrations of saquinavir and ritonavir. Saquinavir should be given with caution in patients receiving rifampicin. Twice-daily dosing or higher saquinavir doses in once-daily administration should be tested to obtain more appropriate plasma levels.

Adverse reactions to first-line antituberculosis drugs

INTRODUCTION

Tuberculosis continues to be a major cause of morbidity and mortality worldwide. Currently available drugs are effective for treatment of the disease or latent infection, but may cause serious adverse effects.

METHODS

The authors reviewed the literature for side effects of five first-line antituberculous medications (isoniazid, rifampin, pyrazinamide, ethambutol and streptomycin). Incidence of the major side effects were compiled with particular attention to the incidence of isoniazid hepatotoxicity.

RESULTS

Hepatotoxicity to isoniazid is a serious problem. Although overall incidence may be decreasing, incidence averaged 9.2 per 1000 patients who were compliant, in multiple studies, with a case fatality rate of 4.7%. The incidence is higher with increasing age. Other serious adverse effects include dermatological, gastrointestinal, hypersensitivity, neurological, haematological and renal reactions. They can lead to drug discontinuation (in up to 10% of patients) or even more serious morbidity or mortality.

CONCLUSIONS

Side effects to antituberculosis drugs are common, and include hepatitis, cutaneous reactions, gastrointestinal intolerance, haematological reactions and renal failure. These adverse effects must be recognised early, to reduce associated morbidity and mortality.

Safety, Efficacy and Pharmacokinetics of Ritonavir 400mg/Saquinavir 400mg Twice Daily plus Rifampicin Combined Therapy in HIV Patients with Tuberculosis

OBJECTIVE

To assess the drug concentrations, efficacy and safety of concomitant use of rifampicin and regimens containing ritonavir/saquinavir (400mg/400mg twice daily) in tuberculosis-HIV treatment-naive patients.

DESIGN AND METHODS

This was an open-label, non-randomised, multiple-dose study. On study day (D)1, tuberculosis treatment (rifampicin 600mg/isoniazid 400mg per day fasting plus pyrazinamide 2 g/day) was introduced in 30 patients. On D31, highly active antiretroviral therapy (HAART) consisting of two nucleoside analogues plus ritonavir/saquinavir 400mg/400mg twice daily was initiated (n = 20). The pharmacokinetics were assayed with a validated reversed-phase HPLC method before the introduction of HAART on D30 (for rifampicin), after 30 days of HAART at D60 (for rifampicin plus ritonavir/saquinavir), and at the end of the study (without rifampicin) on D210 (for ritonavir/saquinavir). Clinical evaluations were performed on a monthly basis. CD4 counts and viral load were collected on D30, D60 and D180. Genotyping test for HIV was collected at baseline and at D180. Primary endpoints were drug concentration and viral load at D180 (<80 copies/mL). Secondary endpoints were presence of grade 3 and serious adverse events, clinical improvement, CD4 count and genotypic resistance to ritonavir/saquinavir.

RESULTS

Ten patients dropped out of the study during tuberculosis therapy alone. Mean (+/- SD) baseline CD4 count (on D30) was 151.89 (+/- 146.77) cells/mm(3) and viral load was 5.34 (+/- 0.4) log. During the antiretroviral therapy, 15 patients dropped out, 14 because of adverse events. One patient (of five) presented a viral load of <80 copies/mL at D180. All but one patient increased CD4 counts from baseline. No genotypic resistance was detected. Clinical improvement was evident in all five patients who tolerated the therapy. Serum concentrations of ritonavir/saquinavir and rifampicin remained within the therapeutic range.

CONCLUSIONS

Therapeutic concentrations of the studied drugs and reduction of viral load were achieved; adverse events are the main limitation of use of a ritonavir/saquinavir regimen in treatment-naive patients, but its clinical benefits were evident.