Susan L. Rosenkranz

The practice orientations of physicians and patients: the effect of doctor–patient congruence on satisfaction

This study investigated the extent to which the individual orientations of physicians and patients and the congruence between them are associated with patient satisfaction. A survey was mailed to 400 physicians and 1020 of their patients. All respondents filled out the Patient-Practitioner Orientation Scale, which measures the roles that doctors and patients believe each should play in the course of their interaction. Patients also rated their satisfaction with their doctors. Among patients, we found that females and those who were younger, more educated, and healthier were significantly more patient-centered. However, none of these variables were significantly related to satisfaction. Among physicians, females were more patient-centered, and years in practice was related to satisfaction and orientation in a non-linear fashion. The congruence data indicated that patients were highly satisfied when their physicians either had a matching orientation or were more patient-centered. However, patients whose doctors were not as patient-centered were significantly less satisfied.

Pharmacokinetic interactions between protease inhibitors and statins in HIV seronegative volunteers: ACTG Study A5047.

Objective Lipid lowering therapy is used increasingly in persons with HIV infection in the absence of safety data or information on drug interactions with antiretroviral agents. The primary objectives of this study were to examine the effects of ritonavir (RTV) plus saquinavir soft-gel (SQVsgc) capsules on the pharmacokinetics of pravastatin, simvastatin, and atorvastatin, and the effect of pravastatin on the pharmacokinetics of nelfinavir (NFV) in order to determine clinically important drug–drug interactions. Design Randomized, open-label study in healthy, HIV seronegative adults at AIDS Clinical Trials Units across the USA. Methods Three groups of subjects (arms 1, 2, and 3) received pravastatin, simvastatin or atorvastatin (40 mg daily each) from days 1–4 and 15–18. In these groups, RTV 400 mg and SQVsgc 400 mg twice daily were given from days 4–18. A fourth group (arm 4) received NFV 1250 mg twice daily from days 1–14 with pravastatin 40 mg daily added from days 15–18. Statin and NFV levels were measured by liquid chromatography/tandem mass spectrometry. Results Fifty-six subjects completed both pharmacokinetic study days. In arms 1–3, the median estimated area under the curves (AUC)0−−24 for the statins were: pravastatin (arm 1, n = 13), 151 and 75 nguu.h/ml on days 4 and 18 (decline of 50% in presence of RTV/SQVsgc), respectively (P = 0.005); simvastatin (arm 2, n = 14), 17 and 548 nguu.h/ml on days 4 and 18 (increase of 3059% in the presence of RTV/SQVsgc), respectively (P < 0.001); and total active atorvastatin (arm 3, n = 14), 167 and 289 nguu.h/ml on days 4 and 18 (increase of 79% in the presence of RTV/SQVsgc), respectively (P < 0.001). In arm 4, the median estimated AUC0−−8 for NFV (24 319 versus 26 760 nguu.h/ml;P = 0.58) and its active M8 metabolite (15 565 versus 14 571 nguu.h/m;P = 0.63) were not statistically different from day 14 to day 18 (without or with pravastatin). Conclusions Simvastatin should be avoided and atorvastatin may be used with caution in persons taking RTV and SQVsgc. Dose adjustment of pravastatin may be necessary with concomitant use of RTV and SQVsgc. Pravastatin does not alter the NFV pharmacokinetics, and thus appears to be safe for concomitant use.

Effect of efavirenz on the pharmacokinetics of simvastatin, atorvastatin, and pravastatin: results of AIDS Clinical Trials Group 5108 Study.

Efavirenz (EFV) is associated with hyperlipidemia when used in combination with other antiretroviral drugs. EFV is a mixed inducer/inhibitor of cytochrome P450 (CYP) 3A4 isozyme and may interact with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors that are primarily metabolized via CYP3A4. To assess the drug-drug interaction of EFV used in combination with simvastatin (SIM), atorvastatin (ATR), or pravastatin (PRA), an open-label trial was conducted in 52 healthy adult HIV-seronegative subjects across AIDS Clinical Trials Group sites in the United States. Subjects received 40 mg of SIM, 10 mg of ATR, or 40 mg of PRA daily on days 0 through 3 and days 15 through 18. EFV was administered daily at a dose of 600 mg on days 4 through 18. SIM, ATR, and PRA concentrations were determined before and after EFV, and EFV concentrations were determined before and after statins. EFV reduced SIM acid exposure (area under the curve at 0 to 24 hours [AUC0-24h]) by 58% (Wilcoxon signed rank test, P = 0.003) and active HMG-CoA reductase inhibitory activity by 60% (P < 0.001). EFV reduced ATR exposure by 43% (P < 0.001) and the total active ATR exposure by 34% (P = 0.005). EFV administration resulted in a 40% decrease in PRA exposure (P = 0.005). SIM, ATR, and PRA had no effect on non-steady-state EFV concentrations. In conclusion, EFV, when administered with SIM, ATR, or PRA, can result in significant induction of statin metabolism. The reduced inhibition of HMG-CoA reductase activity during coadministration of EFV may result in diminished antilipid efficacy at usual doses of SIM, ATR, and PRA.

Population Pharmacokinetics and Pharmacodynamics of Efavirenz, Nelfinavir, and Indinavir: Adult AIDS Clinical Trial Group Study 398

ABSTRACT The present population pharmacokinetic (PK) and pharmacodynamic (PD) study modeled the effects of covariates including drug adherence and the coadministration of protease inhibitors (PIs) on the pharmacokinetics of efavirenz (EFV) and the relationship between EFV exposure and virological failure in patients who failed initial PI treatment in Adult AIDS Clinical Trial Group (AACTG) study 398. We also report on the population PKs of the PIs nelfinavir (NFV) and indinavir (IDV). AACTG study 398 patients received EFV, amprenavir, adefovir dipivoxil, and abacavir and were randomized to take, in addition, one of the following: NFV, IDV, saquinavir (SQV), or placebo. The PK databases consisted of 531 EFV concentrations (139 patients), 219 NFV concentrations (75 patients), and 66 IDV concentrations (11 patients). Time to virological failure was ascertained for all patients in the PK databases. PK data were fit with a population PK model that assumed exclusive hepatic elimination (the well-stirred model). Notable findings with respect to EFV PK and PD are as follows. (i) The hepatic clearance of EFV is unaltered by NFV, IDV, or SQV coadministration. (ii) The hepatic clearance of EFV appears to be 28% higher in white non-Hispanics than in African Americans and Hispanics (P = 0.03). (iii) Higher adherence scores (as measured with the Medication Event Monitoring System) are associated with marginally increased levels of exposure to EFV. (iv) In patients with no prior experience with nonnucleoside reverse transcriptase inhibitors (NNRTIs), a given percent increase in the oral clearance (CL/F) of EFV is associated with a greater percent increase in the hazard of virological failure (P < 0.0003). Among NNRTI-experienced patients, however, hazard is relatively uncorrelated with EFV CL/F.

Modeling HIV dynamics and antiviral response with consideration of time-varying drug exposures, adherence and phenotypic sensitivity.

Highly active antiretroviral therapies consisting of reverse transcriptase inhibitor drugs and protease inhibitor drugs, which can rapidly suppress HIV below the limit of detection, are currently the most effective treatment for HIV infected patients. In spite of this, many patients fail to achieve viral suppression, probably due to existing or developing drug resistance, poor adherence, pharmacokinetic problems and other clinical factors. In this paper, we develop a viral dynamic model to evaluate how time-varying drug exposure and drug susceptibility affect antiviral response. Plasma concentrations, in turn, are modeled using a standard pharmacokinetic (PK) one-compartment open model with first order absorption and elimination as a function of fixed individual PK parameters and dose times. Imperfect adherence is considered as missed doses in PK models. We discuss the analytic properties of the viral dynamic model and study how time-varying treatment efficacies affect antiviral responses, specifically viral load and T cell counts. The relationship between actual failure time (the time at which the viral growth rate changes from negative to positive) and detectable failure time (the time at which viral load rebounds to above the limit of detection) is investigated. We find that an approximately linear relationship can be used to estimate the actual rebound failure time from the detectable rebound failure time. In addition, the effect of adherence on antiviral response is studied. In particular, we examine how different patterns of adherence affect antiviral response. Results suggest that longer sequences of missed doses increase the chance of treatment failure and accelerate the failure. Simulation experiments are presented to illustrate the relationship between antiviral response and pharmacokinetics, time-varying adherence and drug resistance. The proposed models and methods may be useful in AIDS clinical trial simulations.

Modeling long-term HIV dynamics and antiretroviral response : Effects of drug potency, pharmacokinetics, adherence, and drug resistance

We propose a long-term HIV-1 dynamic model by considering drug potency, drug exposure, and drug susceptibility. Using a Bayesian approach, HIV-1 dynamic parameters were estimated by fitting the model to viral load data from a phase 1/2 randomized clinical study of 2 indinavir (IDV)/ritonavir (RTV)-containing highly active antiretroviral (ARV) therapy regimens in HIV-infected subjects who had previously failed protease inhibitor-containing ARV therapies. A large between-subject variation in estimated viral dynamic parameters was observed, even after accounting for variations in drug exposure and drug susceptibility, suggesting that characteristics of HIV-1 dynamics are host dependent. Significant correlations of baseline factors such as HIV-1 RNA levels and CD4+ cell counts with viral dynamic parameters were found. These correlations coincide with biologic interaction mechanisms between HIV and the host immune system and also provide an explanation for the correlations between the baseline viral load and phase 1 viral decay rate, for which inconsistent results have been reported in the literature. The relations between viral dynamic parameters and virologic response were established, and these results suggest that viral dynamic parameters may play an important role in determining treatment success or failure. In particular, we estimated a drug efficacy threshold for each patient that can be used to assess whether an ARV regimen is potent enough to suppress HIV viruses in the individual patient. Our findings indicate that it is necessary to individualize the ARV regimen to treat HIV-1-infected patients. The proposed mathematic models and statistical techniques may provide a framework to simulate and predict antiviral response for individual patients.

Effect of ritonavir/saquinavir on stereoselective pharmacokinetics of methadone : Results of AIDS clinical trials group (ACTG) 401

The effect of ritonavir 400 mg/saquinavir 400 mg twice daily on the stereoselective pharmacokinetics of methadone was examined in 12 HIV‐infected, methadone‐using study subjects. Design: A 24‐hour methadone pharmacokinetic study was performed before antiretroviral therapy was begun and after 15 days of therapy. Methadone concentration was measured by a chiral plasma assay because the drug is administered as a racemic mixture of R‐ and S‐methadone, but only the R‐isomer is active. Both changes in plasma protein binding and changes in objective and subjective opioid effect were monitored. Results: Ritonavir/saquinavir administration was associated with 40% decrease in total S‐methadone AUC0‐24hr and 32% decrease in R‐methadone area under the curve (AUC)0‐24hr, and both changes were statistically significant (p = .001 for both). When AUC was corrected for the changes in protein binding induced by ritonavir/saquinavir, R‐methadone free AUC0‐24hr decreased 19.6% whereas the S‐methadone decreased 24.6%, neither of these changes was statistically significant (p = .129 and p = .0537, respectively). This change in methadone exposure was not associated with any evidence of withdrawal from narcotics and no modification of methadone dose was required. Conclusions: Our data indicate that ritonavir/saquinavir administration is associated with induction of metabolism of methadone but this is greater for the inactive S‐methadone. However, approximately 37% of the decrease in the total R‐methadone exposure can be explained by protein binding displacement. Ritonavir/saquinavir can be used in HIV‐infected people taking methadone without routine dose adjustments.

The Clinical Pharmacokinetics of Rifampin and Ethambutol in HIV-Infected Persons with Tuberculosis

BACKGROUND The pharmacokinetics of rifampin and ethambutol in HIV-infected patients with tuberculosis (TB) are incompletely characterized. We examined the pharmacokinetics of rifampin and ethambutol in a cohort of patients with HIV-related TB who were treated in the United States. METHODS Serum drug concentrations were determined 2, 6, and 10 h after dosing in 36 HIV-infected patients with TB who were taking rifampin and in 49 who were taking ethambutol. Observed serum concentrations were compared with published normal ranges and published data. RESULTS With daily dosing of rifampin (600 mg), 26 (77%) of 34 patients (95% confidence interval [CI], 59%-89%]) had a low maximum concentration of rifampin (<8 microg/mL), and 12 (35%; 95% CI, 20%-54%) had a very low maximum concentration (<4 microg/mL). With intermittent rifampin dosing (600 mg), 13 (68%) of 19 patients (95% CI, 44%-85%) had a low maximum concentration of rifampin, and 5 (26%; 95% CI, 11%-50%) had a very low maximum concentration. With daily ethambutol dosing (20 mg/kg), 33 (69%) of 48 patients (95% CI, 55%-81%) had a low maximum concentration of ethambutol (<2 microg/mL), and 18 (38%; 95% CI, 24%-53%) had a very low maximum concentration (<1 microg/mL). With intermittent ethambutol dosing (50 mg/kg twice weekly or 30 mg/kg thrice weekly), 13 (72%) of 18 patients (95% CI, 47%-88%) had a low maximum concentration of ethambutol (<4 microg/mL), and 5 (28%; 95% CI, 12%-54%]) had a very low maximum concentration (<2 microg/mL). CONCLUSIONS In HIV-infected patients with TB who are receiving rifampin and ethambutol, low maximum concentrations of rifampin and ethambutol were common. For patients with HIV-related TB, therapeutic monitoring of rifampin and ethambutol levels may help clinicians achieve target serum concentrations.

Can small-area analysis detect variation in surgery rates? The power of small-area variation analysis.

A variety of statistical methods can be used in small-area analysis to test whether there is more variation than would be expected by chance alone. However, the power of these methods to detect existing variation has never been studied. The authors used data regarding back surgery in Washington State to suggest several types of variation that might exist (alternative hypotheses), and then used computer simulation to determine the power, or the probability of detecting this variation. The chi-square test had the highest power of all methods considered against most alternative hypotheses. Power is higher if there are no multiple admissions, rates are higher, and counties have larger or similar population size. Problems of accounting for multiple admissions, adjustment for age and sex, choosing the optimum size of small areas, and detection of outliers also are discussed.

Modified Directly Observed Antiretroviral Therapy Compared with Self-Administered Therapy in Treatment-Naïve HIV-1 Infected Patients: A Randomized Trial

BACKGROUND Success of antiretroviral therapy depends on high rates of adherence, but few interventions are effective. Our objective was to determine if modified directly observed therapy (mDOT) improves initial antiretroviral success. METHODS In an open-label, randomized trial comparing mDOT (Monday-Friday for 24 weeks) and self-administered therapy with lopinavir/ritonavir soft gel capsules (800 mg/200 mg), emtricitabine (200 mg), and either extended-release stavudine (100 mg) or tenofovir (300 mg), all taken once daily, 82 participants received mDOT and 161, self-administered therapy. Participant eligibility included a plasma human immunodeficiency virus RNA level higher than 2000 copies/mL and being naïve to antiretroviral therapy. A total of 243 participants were predominantly male (79%) (median age, 38 years), with 84 Latinos (35%), 74 non-Latino blacks (30%), and 79 non-Latino whites (33%). The study was conducted at 23 AIDS Clinical Trials Group (ACTG) sites in the United States and 1 site in South Africa between October 2002 and January 2006. The primary outcome was virologic success at week 24 and secondary outcomes were virologic success, clinical progression, and adherence at week 48. RESULTS Over 24 weeks, mDOT had greater virologic success (0.91; 95% confidence interval [CI], 0.81 to 0.95) than self-administered therapy (0.84; 95% CI, 0.77 to 0.89), but the difference (0.07; lower bound 95% CI, -0.01) did not reach the prespecified threshold of 0.075. Over 48 weeks, virologic success was not significantly different between mDOT (0.72; 95% CI, 0.61 to 0.81) and self-administered therapy (0.78; 95% CI, 0.70 to 0.84) (difference, -0.06; 95% CI, -0.18 to 0.07 [P = .19]). CONCLUSIONS The potential benefit of mDOT was marginal and not sustained after discontinuation. Modified DOT should not be incorporated routinely for care of treatment-naïve human immunodeficiency virus type 1-infected patients.