Peter P. Koopmans

Vitamin D Deficiency among HIV Type 1-Infected Individuals in the Netherlands: Effects of Antiretroviral Therapy

Vitamin D regulates bone metabolism but has also immunoregulatory properties. In HIV-infected patients bone disorders are increasingly observed. Furthermore, low 1,25(OH)(2)D(3) levels have been associated with low CD4(+) counts, immunological hyperactivity, and AIDS progression rates. Few studies have examined the vitamin D status in HIV-infected patients. This study will specifically focus on the effects of antiretroviral agents on vitamin D status. Furthermore, the effect of vitamin D status on CD4 cell recovery after initiation of HAART will be evaluated. Among 252 included patients the prevalence of vitamin D deficiency (<35 nmol/liter from April to September and <25 nmol/liter from October to March) was 29%. Female sex, younger age, dark skin, and NNRTI treatment were significant risk factors in univariate analysis, although in multivariate analyses skin pigmentation remained the only independent risk factor. Median 25(OH)D(3) levels were significantly lower in white NNRTI-treated patients [54.5(27.9-73.8) nmol/liter] compared to white PI-treated patients [77.3 (46.6-100.0) nmol/liter, p = 0.007], while among nonwhites no difference was observed. Both PI- and NNRTI-treated patients had significantly higher blood PTH levels than patients without treatment. Moreover, NNRTI treatment puts patients at risk of elevated PTH levels (>6.5 pmol/liter). Linear regression analysis showed that vitamin D status did not affect CD4 cell recovery after initiation of HAART. In conclusion, 29% of the HIV-1-infected patients had vitamin D deficiency, with skin color as an independent risk factor. NNRTI treatment may add more risk for vitamin D deficiency. Both PI- and NNRTI-treated patients showed higher PTH levels and might therefore be at risk of bone problems. Evaluation of 25(OH)D(3) and PTH levels, especially in NNRTI-treated and dark skinned HIV-1-infected patients, is necessary to detect and treat vitamin D deficiency early.

Pharmacokinetics of Adjusted-Dose Lopinavir-Ritonavir Combined with Rifampin in Healthy Volunteers

ABSTRACT Coadministration of lopinavir-ritonavir, an antiretroviral protease inhibitor, at the standard dose (400/100 mg twice a day [BID]) with the antituberculous agent rifampin is contraindicated because of a significant pharmacokinetic interaction due to induction of cytochrome P450 3A by rifampin. In the present study, two adjusted-dose regimens of lopinavir-ritonavir were tested in combination with rifampin. Thirty-two healthy subjects participated in a randomized, two-arm, open-label, multiple-dose, within-subject controlled study. All subjects were treated with lopinavir-ritonavir at 400/100 mg BID from days 1 to 15. From days 16 to 24, the subjects in arm 1 received lopinavir-ritonavir at 800/200 mg BID in a dose titration, and the subjects in arm 2 received lopinavir-ritonavir at 400/400 mg BID in a dose titration. Rifampin was given at 600 mg once daily to all subjects from days 11 to 24. The multiple-dose pharmacokinetics of lopinavir, ritonavir, and rifampin were assessed. Twelve of 32 subjects withdrew from the study. For nine subjects lopinavir-ritonavir combined with rifampin resulted in liver enzyme level elevations. Pharmacokinetic data for 19 subjects were evaluable. Geometric mean ratios for the lopinavir minimum concentration in serum and the maximum concentration in serum (Cmax) on day 24 versus that on day 10 were 0.43 (90% confidence interval [CI], 0.19 to 0.96) and 1.02 (90% CI, 0.85 to 1.23), respectively, for arm 1 (n = 10) and 1.03 (90% CI, 0.68 to 1.56) and 0.93 (90% CI, 0.81 to 1.07), respectively, for arm 2 (n = 9). Ritonavir exposure increased from days 10 to 24 in both arms. The geometric mean Cmax of rifampin was 13.5 mg/liter (day 24) and was similar between the two arms. Adjusted-dose regimens of lopinavir-ritonavir in combination with therapeutic drug monitoring and monitoring of liver function may allow concomitant use of rifampin.

Carbamazepine–Indinavir Interaction Causes Antiretroviral Therapy Failure

OBJECTIVE: To report a case of antiretroviral therapy failure caused by an interaction between carbamazepine and indinavir. CASE SUMMARY: A 48-year-old HIV-positive white man was treated with antiretroviral triple therapy, consisting of indinavir, zidovudine, and lamivudine. His HIV-RNA (viral load) became undetectable (<400 copies/mL) less than two months after this therapy was started; this was confirmed one month later. Shortly after the start of antiretroviral therapy, the patient developed herpes zoster, which was treated with famciclovir. Tramadol was initially prescribed for postherpetic neuralgia; however, this was substituted with carbamazepine due to insufficient analgesic effect. Indinavir plasma concentrations decreased substantially during carbamazepine therapy. Carbamazepine was stopped after 2.5 months and, two weeks later, the HIV-RNA was detectable (6 times 103 copies/mL). Resistance for lamivudine was observed in that blood sample; resistance for zidovudine might have been present, and resistance to indinavir was not detected. A few months later, a further increase of the HIV-RNA occurred (300 times 103 copies/mL), after which the therapy was switched to a new antiretroviral regimen containing nevirapine, didanosine, and stavudine. DISCUSSION: Physicians may prescribe carbamazepine for HIV-infected patients to treat seizures or postherpetic neuralgia, which are complications of opportunistic infections such as herpes zoster or toxoplasmosis. Carbamazepine is a potent enzyme inducer, predominantly of the CYP3A enzyme system, while HIV-protease inhibitors such as indinavir are substrates for and inhibitors of CYP3A. Therefore, an interaction between these drugs could be expected. A low dose of carbamazepine (200 mg/d) and the usual dose of indinavir (800 mg q8h) in our patient resulted in carbamazepine concentrations within the therapeutic range for epilepsy treatment; indinavir concentrations dropped substantially. The virologic, resistance, and plasma drug concentration data, as well as the chronology of events, are highly indicative of antiretroviral treatment failure due to the interaction between carbamazepine and indinavir. CONCLUSIONS: Concomitant use of carbamazepine and indinavir may cause failure of antiretroviral therapy due to insufficient indinavir plasma concentrations. Drugs other than carbamazepine should be considered to prevent this interaction. Amitriptyline or gabapentin are alternatives for postherpetic neuralgia; valproic acid or lamotrigine are alternatives for seizures. When alternate drug therapy is not possible, dosage adjustments, therapeutic drug monitoring, and careful clinical observation may help reduce adverse clinical consequences.

Possible drug-metabolism interactions of medicinal herbs with antiretroviral agents.

Herbal medicines are widely used by HIV patients. Several herbal medicines have been shown to interact with antiretroviral drugs, which might lead to drug failure. We have aimed to provide an overview of the modulating effects of Western and African herbal medicines on antiretroviral drug-metabolizing and transporting enzymes, focusing on potential herb–antiretroviral drug interactions. Echinacea, garlic, ginkgo, milk thistle, and St. Johns wort have the potential to cause significant interactions. In vitro and in vivo animal studies also indicated other herbs with a potential for interactions; however, most evidence is based on in vitro studies. Further pharmacokinetic studies to unveil potential Western and especially African herb–antiretroviral drug interactions are urgently required, and the clinical significance of these interactions should be assessed.

Randomized trial comparing saquinavir soft gelatin capsules versus indinavir as part of triple therapy (CHEESE study)

OBJECTIVE To compare efficacy and tolerability of saquinavir soft gelatin capsule (SQV-SGC) formulation and indinavir, both given as part of a triple drug regimen containing zidovudine and lamivudine, in HIV-1-infected individuals. DESIGN Randomized, open label, multicentre study. PATIENTS A total of 70 patients who were antiretroviral-naive and who had a CD4 cell count < 500 x 10(6)/I and/or > 10000 HIV RNA copies/ml plasma and/or HIV-related symptoms. Subjects were assigned randomly to zidovudine 200 mg three times per day plus lamivudine 150 mg twice per day plus either SQV-SGC 1200 mg three times per day (SQV-SGC group) or indinavir 800 mg three times per day (indinavir group). Data are presented for all patients up to week 24. RESULTS Mean baseline CD4 cell counts (+/- SE) were 301+/-29 x 10(6) cells/l and 310 +/-43 x 10(6) cells/l in the SQV-SGC and indinavir groups, respectively. The log10 median baseline HIV RNA load was 5.00 copies/ml in the SQV-SGC group and 4.98 copies/ml in the indinavir group. No difference in antiretroviral effect between the treatment arms could be demonstrated. Intention-to-treat analysis (last observation carried forward [LOCF]) at week 24 revealed that RNA levels decreased to < 50 copies/ml in 74.3% of patients in the SQV-SGC group and in 71.4% of the patients in the indinavir group (P = 0.78). In the on-treatment analysis the proportion of patients < 50 copies/ml at week 24 was 88.0% in the SQV-SGC group and 84.6% in the indinavir group (P = 0.725). Intriguingly, the mean increase of CD4 cells in the first 24 weeks was 162+/-20 x 10(6) cells/l in the SQV-SGC group and 89+/-21 x 10(6) cells/l in the indinavir group (P = 0.01), but preliminary data indicate that this difference in CD4 cell count gain may disappear after 24 weeks of treatment. Both regimens were generally well tolerated. CONCLUSION During the first 24 weeks of the study, we found no difference in antiviral potency between the indinavir group and the SQV-SGC group. A significantly higher CD4 response in the SQV-SGC group was observed.

International Interlaboratory Quality Control Program for Measurement of Antiretroviral Drugs in Plasma

ABSTRACT An international interlaboratory quality control program for measurement of antiretroviral drugs was initiated. The first round was confined to protease inhibitors and showed large variability in the performance of participating laboratories. The results demonstrate the need for and utility of an ongoing quality control program in this area of bioanalysis.

A retrospective TDM database analysis of interpatient variability in the pharmacokinetics of lopinavir in HIV-infected adults

Lopinavir is one of the most-widely used protease inhibitors in the treatment of HIV-1 infected patients. Concentration-effect relationships have been described for both antiviral activity and toxicity. Less is known about patient characteristics that may determine interpatient variability in lopinavir plasma concentrations. A database was created containing all Therapeutic Drug Monitoring (TDM) results collected at our Department. Patients were included if they were using lopinavir twice daily for at least two weeks; subjects who were known to be nonadherent (based on either a lopinavir concentration <0.2 mg/L or suspected by the physician) were excluded. Demographic data were collected from TDM application forms and patient charts. Patients attending one of the 22 HIV treatment centers in The Netherlands. The Department of Clinical Pharmacy is a national referral center for TDM of antiretroviral agents. Lopinavir concentration ratios (CRs) were calculated for each patient by dividing the individual plasma concentration by the time-adjusted population value. Relationships with lopinavir CRs were tested using regression analysis and analysis of variance. A total of 802 patients were included (607 males; 150 females; 45 unknown). The age and body weight of the patients ranged from 18 to 74 years (mean 42) and 42 to 121 kg (mean 72), respectively. Race was known for 756 persons: Caucasian 76%, African 18% and Asian 6%. The median (+ interquartile range, IQR) lopinavir CR was 0.98 (IQR: 0.67-1.31). Body weight showed an inverse relationship with lopinavir CR (F = 23.1; P < 0.001). Age was not related with lopinavir CR (P = 0.99). Female patients had a significantly higher lopinavir CR than males: 1.18 vs. 1.03 (P = 0.005); race was not associated with differences in lopinavir CR. In a multivariate regression analysis body weight, but not gender, remained significantly related to lopinavir CR. Body weight is the only demographic factor that could be related to lopinavir exposure; clinicians should be alert for an increased risk of suboptimal antiviral efficacy in patients with high body weight, and for an increased risk of toxicity in patients with a low body weight.

Therapeutic drug monitoring of HIV-protease inhibitors to assess noncompliance.

Objective To determine plasma concentration ratio limits (CORALS) for HIV-protease inhibitors outside of which random plasma concentrations reflect partial compliance or noncompliance. In the absence of a gold standard for measuring compliance and to avoid complex techniques, measuring plasma concentrations may be an objective and easy way to check noncompliance. Methods Pharmacokinetic curves after observed ingestion were recorded in patients on steady-state indinavir 800 mg TID (n = 22), ritonavir 400 mg/saquinavir 400 mg BID (n = 22, ritonavir; n = 17, saquinavir hard-gel capsules), or nelfinavir 750 mg TID (n = 4) or 1250 mg BID (n = 4). Concentration ratios were calculated by dividing the measured concentration by the median population value at the corresponding sampling time. Limits were based on the minimum P05 (5th percentile) and maximum P95 of these ratios found during the sampling interval. With these limits the authors determined (1) the proportion of patients falsely judged as noncompliers after observed ingestion, (2) discrimination between compliers and noncompliers, and (3) the absolute percentage of noncompliers. To judge the last two elements, two sets of random plasma samples were included: (1) samples sent in by the physician on suspicion of noncompliance (indinavir, n = 42; nelfinavir, n = 22;) or from a study population stating imperfect compliance in a questionnaire (ritonavir/saquinavir, n = 11); (2) control samples sent in routinely for monitoring therapeutic levels (indinavir, n = 41; nelfinavir, n = 201) or drawn from patients who stated perfect compliance in the questionnaire (ritonavir/saquinavir, n = 35). Results The following CORALS were found: indinavir <0.23 or >3.3; nelfinavir <0.36 or >2.1; ritonavir <0.18 or >1.9; saquinavir <0.28 or >2.3. In 31% to 55% of the patients suspected of noncompliance a plasma concentration ratio outside these limits was found. If a ratio was outside the limits, there was a 68% to 88% chance that that plasma sample belonged to a patient suspected of noncompliance, compared with the controls (all Chi-squared tests P < 0.05). Compared with observed ingestion, these chances ranged from 87% to 92%. Conclusion By using concentration ratio limits (CORALS), plasma samples of protease inhibitors with values outside these limits are highly indicative of partial or noncompliance.

Effect of low-dose ritonavir (100 mg twice daily) on the activity of cytochrome P450 2D6 in healthy volunteers

In the treatment of human immunodeficiency virus infection, the protease inhibitor ritonavir is used in a low dose (100 mg twice daily) to inhibit cytochrome P450 (CYP) 3A4 and thereby increase plasma concentrations of coadministered protease inhibitors. When applied in a therapeutic dose (600 mg twice daily), ritonavir also inhibits CYP2D6. The effect of low‐dose ritonavir on CYP2D6 is unknown and was investigated in this study.

The Effect of Atazanavir and Atazanavir/Ritonavir on UDP‐Glucuronosyltransferase Using Lamotrigine as a Phenotypic Probe

Atazanavir (ATV) is known to inhibit UGT1A1‐mediated glucuronidation. Here we report the effect of ATV and ATV/ritonavir (RTV) on another UGT1A isoenzyme, UGT1A4. Twenty‐one healthy volunteers received a single dose of 100 mg of oral lamotrigine on days 1, 13, and 27; on each occasion blood was sampled before the dose was administered and through 120 h after ingestion of the drug. On days 8–17 the subjects received oral ATV 400 mg q.d. On days 18–30 the subjects received oral ATV 300 mg plus oral RTV 100 mg q.d. Seventeen subjects were evaluable for pharmacokinetic analysis. Geometric mean ratios (+90% confidence intervals (CIs)) of lamotrigine area under the plasma concentration‐time curve (AUC)0–inf and peak plasma concentration (Cmax) for ATV + lamotrigine and for lamotrigine alone were 0.88 (0.86–0.91) and 0.99 (0.95–1.02), respectively; the corresponding ratios for ATV/RTV and for lamotrigine were 0.68 (0.65–0.70) and 0.94 (0.90–0.97), respectively. The mean ratio of lamotrigine‐2N‐glucuronide to lamotrigine AUC0–inf increased from 0.45 for lamotrigine to 0.71 for ATV/RTV + lamotrigine. ATV alone does not significantly influence glucuronidation of lamotrigine. In contrast, ATV/RTV results in moderately decreased exposure to lamotrigine.