Indinavir did not increase the short-term risk of adverse cardiovascular events relative to nucleoside reverse transcriptase inhibitor therapy in four phase III clinical trials

Vascular dysfunction and cardiovascular complications

PURPOSE OF REVIEW

Antiretroviral (ARV) therapy has altered the course of HIV disease and dramatically increased the lifespan of HIV-infected individuals. Accumulating evidence, however, suggests that prolonged ARV use contributes to metabolic and cardiovascular changes. Understanding the toxicities of ARV treatment and sequelae of long-term infection is critical. This review will examine recent evidence related to vascular dysfunction and cardiovascular complications in HIV infection.

RECENT FINDINGS

Recent studies investigating circulating markers of inflammation, surrogate markers of subclinical atherosclerotic disease, and novel imaging modalities suggest the presence of endothelial dysfunction in HIV-infected patients. In addition, data from several recently updated cohort studies confirm an association between ARV therapy and cardiovascular events.

SUMMARY

New data suggest that cardiovascular disease is increased among HIV-infected patients receiving highly active ARV therapy. The mechanisms of increased cardiovascular disease may relate to direct effects of the HIV virus and inflammation on the vasculature or to toxicities from specific ARV therapies, which may increase traditional cardiovascular risk factors. Understanding and modifying these risks and preventing cardiovascular events are critical to the long-term management of the HIV-infected patient.

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.

Indinavir did not further increase mean triglyceride levels in HIV-infected patients treated with nucleoside reverse transcriptase inhibitors: an analysis of three randomized clinical trials

OBJECTIVES

Metabolic abnormalities including hyperlipidemia have developed in patients infected with the human immunodeficiency virus (HIV) after treatment with protease inhibitor drugs. It is unclear whether the deleterious effects on plasma triglyceride concentrations observed in patients receiving highly active antiretroviral therapy are a class effect of protease inhibitors. Hypertriglyceridemia may constitute a risk factor for cardiovascular disease. The purpose of this retrospective analysis of HIV-infected patients enrolled in three randomized, double-blind trials of indinavir therapy was to determine whether indinavir use was associated with a larger increase in triglyceride levels than treatment without a protease inhibitor.

METHODS

Using a mixed-effects model, we compared average changes in nonfasting plasma triglyceride levels among randomized treatment groups for each protocol separately.

RESULTS

The median increase in triglyceride levels during the 1st year of antiretroviral monotherapy was less with indinavir than with either zidovudine or stavudine. The combination of indinavir and nucleoside-analogue reverse-transcriptase inhibitors (NRTI) resulted in smaller increments in triglyceride levels than NRTI monotherapy. Indinavir also augmented the reduction in triglyceride levels observed with combination therapy using zidovudine and lamivudine in persons with far advanced HIV-infection. However, up to 7% of patients receiving a NRTI and indinavir experienced elevations of nonfasting triglyceride levels in excess of 750 mg/dl.

CONCLUSIONS

On average, the combination of indinavir and NRTI therapy was not associated with a greater elevation of non-fasting triglyceride levels in HIV-infected men with at least moderately advanced immunosuppression than treatment with NRTI drugs alone.

Incidence of myocardial infarction in randomized clinical trials of protease inhibitor-based antiretroviral therapy: an analysis of four different protease inhibitors

Protease inhibitor (PI) therapy for patients infected with the human immunodeficiency virus has been associated with lipid disorders and insulin resistance. We compared the incidence of myocardial infarction (MI) among participants receiving treatment with PIs with or without nucleoside reverse transcriptase inhibitors (nRTIs) to nRTI therapy alone in 30 phase II/III double-blind, randomized studies conducted before 1999 for the first 4 PI drugs. In most trials included in this analysis, participants could receive combination therapy with a PI plus nRTIs in open-label extensions after the blinded phase concluded. Person-years (PY) of follow-up were calculated from treatment initiation to the diagnosis of MI, or to the end of the randomized phases for nRTI-only therapy or to the conclusion of the studies for PI-containing regimens. Separate analyses were conducted for the randomized and the randomized-plus-extension phases. Among 10,986 participants, 7951 (72%) received PI drugs at some point for an average duration of 12 months. There were 10 MIs (1.31/1000 PY) in the randomized phases and 19 MIs (1.63/1000 PY) in the randomized-plus-extension phases. The overall stratified relative risk of MI for PI-containing (1.82 MI/1000 PY) versus nRTI-only (1.05 MI/1000 PY) regimens of 1.69 was not significantly increased (95% confidence interval [CI], 0.54 to 7.48). The absolute difference in MI risk was +0.77 (95% CI, -0.71 to +2.26) MIs/1000 PY. Compared with NRTI-only therapy, patients receiving PI-containing regimens for an average of 1 year did not have significantly more MIs, but the upper bound of the 95% CI indicates there may be up to 2.3 additional MIs per 1000 PY. Although studies with a longer duration of PI therapy are in progress to assess whether a later increase in MI incidence occurs, our analysis did not demonstrate a dramatic increase in MI risk during the first year of PI therapy.

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.

COX-2 selective inhibitors: analysis of the renal effects

COX-2 selective inhibitors provide analgesia and blunt inflammation while also sparing the gastrointestinal tract from classic NSAID toxicity. Therapeutic effects are thought to result from inhibition of the inflammatory COX-2 isoform. Organ sparing is considered the result of preservation of homeostatic COX-1 enzyme function. Similar roles of the COX isoforms in the kidney would reduce NSAID-associated nephrotoxicity. However, human kidney tissue expresses COX-2 enzyme, suggesting a role for this isoform in maintenance of physiological renal processes. Available clinical data on the renal effects of COX-2 selective inhibitors in humans also demonstrate nephrotoxic potential.

Hyperlipidemia in HIV-positive patients receiving antiretrovirals

OBJECTIVE

To assess the frequency of lipid abnormalities and treatment outcomes for hyperlipidemia in HIV-positive patients receiving antiretroviral (ARV) therapy as outpatients at a Veterans Affairs HIV clinic.

METHODS

All patients monitored for at least 3 months were reviewed. Data collected included age, most recent CD4+ cell count and viral load, ARV history, and all fasting cholesterol, triglyceride, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) values. The ARV therapy at the time of lipid readings was classified as including protease inhibitors (PI+) or not including them (PI-). Lipid values were compared with goals per national guidelines and risk factors.

RESULTS

Male patients (n = 101) providing 210 lipid profiles were evaluated (median 2 per patient). Median age was 51 years. Fourteen patients were diabetic, 31 were hypertensive, and 6 patients had documented coronary disease. Mean cholesterol, triglycerides, and LDL values were significantly higher in PI+ (n = 50) compared with those of PI- patients (n = 51; p < 0.05). HDL values were not different between groups. Significantly more PI+ patients had lipid concentrations above recommended goals compared with PI- patients (17 vs. 7; p = 0.04). Six patients achieved lipid goals after following a low-fat diet (4 PI+). Fifteen subjects (11 PI+) were being treated with medications. Ten patients (67%) reached lipid goals, 2 had not reached goals (13%), and 3 (20%) were undergoing medication titration.

CONCLUSIONS

Our HIV-infected patients had significantly higher cholesterol, triglyceride, and LDL values when PI+. In contrast to other reports, the majority of patients treated for lipid abnormalities achieved treatment goals.