Rosa M. Lopez

Pharmacokinetic interaction between nevirapine and rifampicin in HIV-infected patients with tuberculosis

To determine whether rifampicin reduces serum concentrations of nevirapine and whether nevirapine modifies serum concentrations of rifampicin, levels of these agents were determined at steady state by high-performance liquid chromatography in 10 HIV-infected patients with tuberculosis. The median area under the curve (AUC) 0-12h of nevirapine before and after rifampicin was 56.2 and 32.8 microg/ml per hour, respectively ( p =.04). This represents a 31% reduction in serum nevirapine concentrations. The C(max) decreased from 5.6 to 4.5 microg/ml ( p =.04), which represented a 36% reduction. A 21% decrease in the C(min) was not statistically significant. Exposure to rifampicin did not significantly differ between those patients who were receiving and were not receiving nevirapine. However, our study shows that rifampicin reduces serum exposure to nevirapine. The clinical implications for this reduction remain to be established. Given that the lowest trough serum concentration of nevirapine exceeded by more than 40 times the protein binding adjusted median infective dose (IC(50)) of wild-type HIV in all patients, we suggest that there is no need to increase nevirapine dosage when it is given with rifampicin.

Nebulized amphotericin B concentration and distribution in the respiratory tract of lung-transplanted patients.

Background. A criticism of using nebulized amphotericin B (nAB) as prophylaxis against Aspergillus infection after lung transplantation is the lack of knowledge of its pharmacokinetics and distribution in the lung. The aim of this study was to ascertain the concentrations and distribution of nAB in the respiratory tract of patients receiving lung transplantations. Methods. In the drug-concentration study, 120 bronchoscopies were performed in 39 patients receiving lung transplantions after administration of 6 mg of nAB once daily for a minimum of 7 days. Mean nAB concentration in bronchial aspirated secretions (BAS) and bronchoalveolar lavage (BAL) was determined at 4, 12, 24, and 48 hours postnebulization. In the distribution study, 17 patients inhaled 6 mg of 99mtechnetium-labeled AB, and pulmonary distribution was measured using a gamma camera. Pulmonary perfusion was also measured. Both tests were quantitatively evaluated. Results. In the drug-concentration study, mean concentrations of 1.46 &mgr;g/mL in BAS and 15.75 &mgr;g/mL in BAL were reached at 4 hours. At 24 hours, concentrations were 0.37 &mgr;g/m and 11.02 &mgr;g/mL in BAS and BAL, respectively. In the distribution study, 99mtechnetium-labeled AB distribution was uniform in 12 of 13 allografts without bronchiolitis obliterans syndrome (BOS) and in 1 of 4 allografts with BOS. A close correlation was observed between regional drug distribution and regional perfusion (r =0.82, P <0.01). Conclusions. nAB concentrations remained high for the first 24 hours in BAL and for less time in BAS, with distribution of the drug being uniform in patients without BOS. Furthermore, lung-perfusion studies appear to be useful to ascertain nAB distribution in patients receiving lung transplantions.

Nebulized liposomal amphotericin B prophylaxis for Aspergillus infection in lung transplantation: pharmacokinetics and safety.

BACKGROUND The main problem with using nebulized liposomal amphotericin (n-LAB) as prophylaxis for Aspergillus infection after lung transplantation is the lack of knowledge of its pharmacokinetics and its possible adverse effects. The aim of this study was to measure post-inhalation amphotericin B concentration in the respiratory tract and serum of lung transplant patients and assess the effects of n-LAB on respiratory function. METHODS Thirty-two consecutive bronchoscopies were performed on 27 lung transplant patients at two hospitals. Amphotericin B concentration in the first and third aliquot of bronchoalveolar lavage material was measured in steady state. The first aliquot approximates most closely the true amphotericin B concentrations in the proximal airway, whereas the third aliquot provides an optimum sample from the distal airway. RESULTS At 2 days, mean amphotericin B concentrations were 11.1 microg/ml (95% confidence interval [CI]: 16.5 to 5.7 microg/ml) and 9.0 microg/ml (95% CI: 14.3 to 3.8 microg/ml) in the first and third aliquot, respectively. Thereafter, concentrations declined progressively. At 14 days, concentrations were 3.0 microg/ml (95% CI: 4.4 to 1.5 microg/ml) in the first aliquot and 4.1 microg/ml (95% CI: 6.1 to 2.1 microg/ml) in the third aliquot (p = not statistically significant). Traces of amphotericin B (0.1 microg/ml) were found in serum samples from only 1 of 27 patients. Mean value of forced expiratory volume in the first second (FEV(1)) was similar before and after n-LAB. CONCLUSIONS Amphotericin B concentrations after n-LAB remained high for 14 days, at adequate concentrations for prophylaxis of Aspergillus infection. No significant systemic absorption of amphotericin B was detected and no effect was observed on respiratory function. This promising prophylactic regimen warrants assessment in future clinical studies.

Steady-State Pharmacokinetics of a Double-Boosting Regimen of Saquinavir Soft Gel plus Lopinavir plus Minidose Ritonavir in Human Immunodeficiency Virus-Infected Adults

ABSTRACT Management of treatment-experienced human immunodeficiency virus patients has become complex, and therapy may need to include two protease inhibitors at therapeutic doses. The objective of this study was to characterize the pharmacokinetics in serum of saquinavir (1,000 mg twice daily [b.i.d.]), lopinavir (400 mg b.i.d.), and ritonavir (100 mg b.i.d.) in a multidrug rescue therapy study and to investigate whether steady-state pharmacokinetics of lopinavir-ritonavir are affected by coadministration of saquinavir. Forty patients were included (25 given ritonavir, lopinavir, and saquinavir and 15 given ritonavir and lopinavir). The median pharmacokinetic parameters of lopinavir were as follows: area under the concentration-time curve from 0 to 12 h (AUC0-12), 85.1 μg/ml · h; maximum concentration of drug in serum (Cmax), 10.0 μg/ml; trough concentration of drug in serum (Ctrough), 7.3 μg/ml; and minimum concentration of drug in serum (Cmin), 5.5 μg/ml. Lopinavir concentrations were similar in patients with and without saquinavir. The median pharmacokinetic parameters for saquinavir were as follows: AUC0-12, 22.9 μg/ml · h; Cmax, 2.9 μg/ml; Ctrough, 1.6 μg/ml; and Cmin, 1.4 μg/ml. There was a strong linear correlation between lopinavir and ritonavir and between saquinavir and ritonavir concentrations in plasma. The correlation between lopinavir and saquinavir levels was weaker. We found higher saquinavir concentrations in women than in men, with no difference in lopinavir levels. Only patients with very high body weight presented lopinavir and saquinavir concentrations lower than the overall group. Ritonavir has a double-boosting function for both lopinavir and saquinavir, and in terms of pharmacokinetics, the drug doses selected seemed appropriate for combining these agents in a dual protease inhibitor-based antiretroviral regimen for patients with several prior virologic failures.

Atazanavir and lopinavir/ritonavir: pharmacokinetics, safety and efficacy of a promising double-boosted protease inhibitor regimen.

Objective:To assess the pharmacokinetics and tolerability of lopinavir (LPV), ritonavir (RTV) and atazanavir (ATV) as a double-boosted protease inhibitor regimen in HIV-infected adults. Methods:Sixteen patients who started LPV/RTV (400/100 mg b.i.d.) and ATV (300 mg q.d.) were enrolled in the study group (arm A). LPV pharmacokinetics were compared to those of two historical groups: arm B, 15 patients who received LPV/RTV (400/100 mg b.i.d.); and arm C, 25 patients who received LPV/RTV/saquinavir (SQV) (400/100/1000 mg b.i.d.). ATV pharmacokinetics were compared to those of 15 consecutive patients who received ATV and RTV (300/100 mg q.d.) (arm D). Drug concentrations were measured by HPLC. Results:LPV concentrations were significantly higher in arm A than in arms B and C. Median (interquartile range) LPV area under the curve (AUC)0–12 values were 115.7 (99.8–136.5), 85.2 (68.3–109.2) and 85.1 (60.6–110.1) μg/h/ml, respectively. Cmax values were 12.2 (10.7–14.5), 9.5 (6.8–13.9) and 10.0 (6.9–13.6) μg/ml, respectively. Cmin values were 9.1 (7.1–10.4), 5.6 (4.7–8.2) and 5.5 (4.2–7.5) μg/ml, respectively. No difference was observed for ATV AUC0–24 or Cmax between arms A and D. ATV Cmin values were 1.07 (0.61–1.79) in arm A and 0.58 (0.32–0.83) in arm D (P = 0.001). Treatment was not discontinued in any patient because of adverse effects. At 24 weeks, viral load was < 50 copies/ml in 13 of 16 patients. Conclusions:The combination of ATV and LPV/RTV provided high plasma concentrations of both PI, which seemed to be appropriate for patients with multiple prior therapeutic failures, yielding good tolerability and substantial antiviral efficacy.

Evaluation of a limited sampling strategy to estimate area under the curve of tacrolimus in adult renal transplant patients.

Limited sampling strategies have been developed to predict full AUCs. The goal of this study was to develop a limited sampling strategy to estimate the AUC of tacrolimus in adult renal transplant patients and to evaluate its predictive performance in an independent patient population. A total of 27 tacrolimus pharmacokinetic profiles were studied. Blood samples were collected before the dose (0) and at 0.5, 1, 2, 4, 6, 8, and 12 hours postdose. The study was divided into 2 phases. In phase 1, the goal was to obtain a sampling strategy from 14 pharmacokinetic profiles. In phase 2, the bias and precision of the model were evaluated in another 13 pharmacokinetic profiles. The best correlation was achieved at 4 hours after dose (r2 = 0.790). Stepwise multiple regression analysis determined that the abbreviated AUC at 0, 1, and 4 hours could accurately predict total AUC (r2 = 0.965). The following formula was developed: AUC = 8.90 + 4.0C0h+ 1.77C1h + 5.47C4h. No significant differences were found between calculated and estimated AUC (165.6 ± 41.1 and 166.7 ± 43.2 ng·h/mL, respectively). The mean prediction error (MPE), the relative prediction error (PE), and the mean squared error (MSE) were 0.48 ng·h/mL, 0.16%, and 40.0 ng·h/mL, respectively. The limited sampling with use of the 3 levels at 0, 1, and 4 hours postdose provides accurate, reliable determination of tacrolimus AUC in renal transplant patients.

Changes in vancomycin pharmacokinetics during treatment.

Using data gathered in routine monitoring, the pharmacokinetics of vancomycin during the first 10 days of treatment were compared with the pharmacokinetics after 10 days of treatment in 46 adult patients with normal renal function, ages 17-85 years old (mean +/- SD: 50.8 +/- 17.5). The mean time from initiation of treatment to the first sample determination was 5.5 days, and the mean time to the second determination was 13.4 days. Statistical differences between the two periods were observed for all pharmacokinetic parameters, except for the steady-state distribution volume. After 10 days of treatment, the mean +/- SD of the vancomycin clearance and elimination rate constant decreased from 1.31 +/- 0.82 to 1.13 +/- 0.72 ml/kg/min (p = 0.0044) and from 0.13 +/- 0.08 to 0.10 +/- 0.06 h-1 (p = 0.091), respectively. The half-life (t1/2) increased from 8.01 +/- 6.82 to 10.02 +/- 8.00 h (p = 0.012). The median percentage of the increment of t1/2 was 9.4%. The increase in t1/2 was > 50% in 12 patients and > 100% in nine cases. No association was found between the increment of t1/2 and the cumulative vancomycin dose. Frequent monitoring of serum vancomycin seems indicated, given the risk of decreased elimination during prolonged treatment.

Once-daily regimen of saquinavir, ritonavir, didanosine, and lamivudine in HIV-infected patients with standard tuberculosis therapy (TBQD Study).

Objectives:To assess the efficacy and safety of a once-daily regimen with didanosine, lamivudine, saquinavir, and low-dose ritonavir in antiretroviral (ARV)-naive patients with tuberculosis treated with rifampin and the influence of rifampin on plasma trough concentration (Ctrough) of saquinavir. Methods:Single-arm, prospective, multicenter, open-label pilot study, including 32 adult ARV-naive subjects with HIV infection and tuberculosis under standard treatment that included rifampin (600 mg q.d.) and isoniazid (300 mg q.d.). After 2 months of tuberculosis treatment, patients were started on once-daily ARV therapy, consisting of didanosine, lamivudine, ritonavir (200 mg), and saquinavir soft gel capsules (1600 mg). HIV RNA level, CD4 cell count, clinical and laboratory toxicity, and saquinavir Ctrough during and after antituberculosis therapy were analyzed. Results:After 48 weeks of follow-up, 20 of 32 patients (62.5%; 95% CI: 45.8% to 79.2%) in the intent-to-treat population and 20 of 28 (71.4%; 95% CI: 54.4% to 88.4%) in the on-treatment population had an HIV RNA level <50 copies/mL. Treatment tolerance was acceptable in all patients except for 2 with biologic hepatic toxicity leading to discontinuation. Seven patients had virologic failure. In 10 patients (36%), saquinavir Ctrough was <0.05 μg/mL during tuberculosis therapy and 5 of them had virologic failure. The median saquinavir Ctrough was 44% lower (interquartile range: 19% to 71%) with coadministration of rifampin than without. Conclusion:The combination of didanosine, lamivudine, saquinavir, and ritonavir may be a useful treatment regimen for patients with tuberculosis in whom a once-daily protease inhibitor-containing regimen is considered indicated. Nevertheless, on the basis of pharmacokinetic profile the dose of 1600/200 mg of saquinavir/ritonavir cannot be recommended. Further studies with higher doses of saquinavir (2000 mg) boosted with ritonavir are warranted.

Rifampin Reduces Concentrations of Trimethoprim and Sulfamethoxazole in Serum in Human Immunodeficiency Virus-Infected Patients

ABSTRACT To determine whether rifampin reduces concentrations of trimethoprim (TMP) and sulfamethoxazole (SMX) in serum of human immunodeficiency virus (HIV)-infected persons, levels of these agents were determined by high-performance liquid chromatography before and after more than 12 days of standard antituberculosis treatment for 10 patients who had been taking one double-strength tablet of co-trimoxazole once daily for more than 1 month. Statistically significant, 47 and 23% decreases in TMP and SMX mean areas under the concentration-time curve from 0 to 24 h (AUC0–24), respectively, were observed after administration of rifampin.N-Acetyl-SMX profiles without and with rifampin were similar. The steady-state AUC0–24 metabolite/parent drug ratio increased by 32% with rifampin administration. Our study shows that rifampin reduces profiles of TMP and SMX in serum of HIV-infected patients.

Hematocrit influences immunoassay performance for the measurement of tacrolimus in whole blood

The comparison between the MEIA II and the EMIT assays for tacrolimus measurement and the interference by the hematocrit were evaluated in 93 samples from routine therapeutic monitoring at tacrolimus concentrations less than 9 μg/L (group A). Additionally, the incidence of false-positive results were determined in samples (n = 46) from patients who were not receiving the drug (group B). In group A, no statistical differences were observed between the mean ± SD values obtained by MEIA II (5.14 ± 2.28 μg/L) and EMIT (4.61 ± 1.79 μg/L). The correlation coefficient and the regression equation (95% CI) between both assays, were 0.761 and EMIT = 1.088 (0.90, 1.35) MEIA II −0.38 (−1.65, −0.46), respectively. When the samples were stratified according to the hematocrit, the median differences between the methods (MEIA II minus EMIT) were as follows: hematocrit ≤25%, 0.45 μg/L; hematocrit 25%-35%, 0.30 μg/L; and hematocrit >35%, 0.25 μg/L (P = 0.02). In group B, false-positive results (above the detection limit) were observed in 63.04% of samples analyzed by MEIA II and in 2.17% of samples analyzed by EMIT. The median differences in apparent tacrolimus results were significantly higher in the samples with the lowest hematocrit: 2.2 μg/L, 1.4 μg/L, and 0.0 μg/L in samples with hematocrit ≤25%, 25%-35%, and >35%, respectively. In conclusion, the differences in the tacrolimus results obtained by MEIA and EMIT assays were higher in samples from patients with hematocrit less than 25%, and the MEIA assay demonstrated a high incidence of false-positive results.