Biomedical subjects

Scott R Penzak

Publications and source records attributed to Scott R Penzak.

22 records · Page 2Linked to original sources

PubMed2002

Effect of Seville orange juice and grapefruit juice on indinavir pharmacokinetics.

Considerable interpatient variability in indinavir pharmacokinetics, possibly due in part to variable metabolism of the drug through intestinal cytochrome P450 (CYP) 3A4, may contribute to poor virologic response in certain individuals with HIV infection. The purpose of this study was to characterize the influence of intestinal CYP3A4 modulation with grapefruit juice and Seville orange juice on indinavir pharmacokinetics. In an open-label, three-period crossover study, 13 healthy volunteers received indinavir 800 mg every 8 hours for 1 day and a single 800 mg dose the next morning. The last two indinavir doses were taken with 8 ounces of Seville orange juice, single-strength grapefruit juice, or water (control). Plasma samples were collected at time 0 (predose) and at 0.5, 1, 2, 3, 4, and 5 hours after the last indinavir dose. Concentration-time data were analyzed using noncompartmental methods. Coadministration of Seville orange juice and indinavir resulted in a statistically significant increase in indinavir t(max) (1.87 [1.65-2.22] vs. 1.25 [1.03-1.60] h; p < 0.05) without altering other pharmacokinetic parameter values. Grapefruit juice administration did not result in any changes in indinavir pharmacokinetics. Modulation of intestinal CYP3A4 by grapefruit juice and Seville orange juice did not alter the systemic availability of indinavir. The contribution of presystemic metabolism to indinavir interpatient variability appears to be small.

Adult↗

PubMed2002

Risk-benefit of HMG-CoA reductase inhibitors in the treatment of HIV protease inhibitor-related hyperlipidaemia.

HIV protease inhibitors decrease mortality and improve quality of life in patients with HIV infection. However, these drugs have been associated with serum lipid elevations, which may pose an increased risk of cardiovascular disease and pancreatitis. Treatment of protease inhibitor-related hyperlipidaemia (PIH) is complicated by drug interactions, which significantly increase concentrations of most 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins). Although pravastatin and atorvastatin effectively lower cholesterol and triglyceride concentrations in HIV-infected patients, a significant number of patients did not achieve their National Cholesterol Education Program low density lipoprotein concentration goals. Nonetheless, due to the increased risk of rhabdomyolysis with elevated statin concentrations, atorvastatin should be considered a second-line agent. The limited available PIH data supports the fact that pravastatin and atorvastatin are well-tolerated in HIV-infected individuals. More data are needed on the appropriate starting doses, maximum safe doses, role of combination statin-fibrate therapy, documentation of coronary heart disease benefit and incidence of myotoxicity and hepatotoxicity. Pravastatin has an acceptable risk-benefit ratio in PIH, while theoretical toxicity concerns exist with atorvastatin.

Adult↗

PubMed2002

Characterizing and predicting amphotericin B-associated nephrotoxicity in bone marrow or peripheral blood stem cell transplant recipients.

STUDY OBJECTIVE: To characterize amphotericin B-associated nephrotoxicity and to determine the variables associated with it that can be used to identify, a priori, at-risk patients. DESIGN: Retrospective analysis. SETTING: University hospital. PATIENTS: A homogeneous population of 69 recipients of a bone marrow (BMT) or peripheral blood stem cell transplant (PBSCT) with multiple myeloma and who received at least two doses of amphotericin B deoxycholate from January 1, 1992-January 1, 1995. INTERVENTION: Data on demographics, prior and concomitant nephrotoxic drug therapy, daily laboratory values, and amphotericin B dosing were collected serially from medical and pharmacy records. MEASUREMENTS AND MAIN RESULTS: Forward stepwise logistic regression analysis was performed on the data from the first day of therapy to characterize and determine variables related to amphotericin B-associated nephrotoxicity. Nephrotoxicity occurred in 30 patients (43%) and developed rapidly Patients who developed nephrotoxicity were similar to those who did not in many aspects associated with their treatment. However, baseline estimated creatinine clearance, cyclosporine therapy, nephrotoxic drug therapy within 30 days of starting amphotericin B, and the number of concomitant nephrotoxic drugs were significant predictors of amphotericin B-associated nephrotoxicity. CONCLUSION: Recipients of a BMT or PBSCT who have multiple myeloma and are receiving cyclosporine or multiple nephrotoxic drugs at the start of amphotericin B therapy should be considered at high risk for developing amphotericin B-associated nephrotoxicity. Also, because amphotericin B-associated nephrotoxicity develops rapidly, clinicians should be aware of the rapid changes in serum creatinine and electrolyte levels that can occur.

Amphotericin B↗

PubMed2002

Management of protease inhibitor-associated hyperlipidemia.

Dyslipidemia, characterized by elevated serum levels of triglycerides and reduced levels of total cholesterol, low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol, has been recognized in patients with human immunodeficiency virus (HIV) infection. It is thought that elevated levels of circulating cytokines, such as tumor necrosis factor-alpha and interferon-alpha, may alter lipid metabolism in patients with HIV infection. Protease inhibitors, such as saquinavir, indinavir and ritonavir, have been found to decrease mortality and improve quality of life in patients with HIV infection. However, these drugs have been associated with a syndrome of fat redistribution, insulin resistance, and hyperlipidemia. Elevations in serum total cholesterol and triglyceride levels, along with dyslipidemia that typically occurs in patients with HIV infection, may predispose patients to complications such as premature atherosclerosis and pancreatitis. It has been estimated that hypercholesterolemia and hypertriglyceridemia occur in greater than 50% of protease inhibitor recipients after 2 years of therapy, and that the risk of developing hyperlipidemia increases with the duration of treatment with protease inhibitors. In general, treatment of hyperlipidemia should follow National Cholesterol Education Program guidelines; efforts should be made to modify/control coronary heart disease risk factors (i.e. smoking; hypertension; diabetes mellitus) and maximize lifestyle modifications, primarily dietary intervention and exercise, in these patients. Where indicated, treatment usually consists of either pravastatin or atorvastatin for patients with elevated serum levels of LDL-C and/or total cholesterol. Atorvastatin is more potent in lowering serum total cholesterol and triglycerides compared with other hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, but it is also associated with more drug interactions compared with pravastatin. Simvastatin and lovastatin are significantly metabolized by cytochrome P450 enzymes (CYP3A4) and are therefore not recommended for coadministration with protease inhibitors. A fibric acid derivative (gemfibrozil or fenofibrate) should be used in patients with primary hypertriglyceridemia. However, it must be kept in mind that protease inhibitors, such as nelfinavir and ritonavir, induce enzymes involved in the metabolism of the fibric acid derivatives and may, therefore, reduce the lipid-lowering activity of coadministered gemfibrozil or fenofibrate. In certain patients HMG-CoA reductase inhibitors may be used in combination with fibric acid derivatives but patients should be carefully monitored for liver and skeletal muscle toxicity. Select patients may experience improvements in serum lipid levels when their offending protease inhibitor(s) is/are exchanged for efavirenz, nevirapine, or abacavir; however each patient's virologic and immunologic status must be taken closely into consideration.

Clinical Trials as Topic↗