Effects of low-dose simvastatin therapy on serum lipid levels in patients with moderate hypercholesterolemia: a 12-month study. The Simvastatin Study Group

The Adherence Rate Threshold is Drug Specific

Introduction

Patient adherence to a medication regimen is usually expressed as an adherence rate, defined as the proportion of prescribed doses actually taken. An adherence rate threshold, above which the therapeutic effect is maintained, is typically assigned an arbitrary value, commonly 0.8.

Objective

Here, we determined the value of the adherence rate threshold objectively in different drugs of the same class, using statins as an example.

Methods

We used pharmacokinetic/pharmacodynamic (PK/PD) modeling to predict serum levels of low-density lipoprotein cholesterol (LDL-C) in patients taking simvastatin 20 mg or atorvastatin 5 mg once daily for 30 days. LDL-C reduction was modeled for adherence rates of 1.0, 0.8, 0.6, 0.4, and 0.2. The results were expressed as the percentage of time spent at the LDL-C goal (< 70 mg/dL). The adherence rate threshold was defined as the minimum adherence rate that resulted in the same amount of time at goal as perfect adherence (i.e., a rate of 1.0).

Results

For simvastatin, an adherence rate of 0.8 resulted in a significant decrease in time at the LDL-C goal compared to perfect adherence (54.8% versus 85.1%; P < 0.001), and rates < 0.8 resulted in progressively less time at goal. For atorvastatin, the rates of 0.8 and 0.6 resulted in essentially the same amount of time at goal as perfect adherence (87.8% and 87.7%, respectively, versus 88.1%; P > 0.05 for both), with less time at goal only occurring at rates ≤ 0.4 (P < 0.001). Thus, the adherence rate thresholds are > 0.8 for simvastatin and between 0.4 and 0.6 for atorvastatin.

Conclusion

These results indicate that a value of 0.8 cannot be applied universally.

Statin dose in Asians: is pharmacogenetics relevant?

Historically the efficacy and safety of statins has mostly been studied in western populations. Few such studies have been carried out in Asians until recent years. These studies revealed interesting similarities and differences for statin use between Asians and Caucasians. One clinically important question subsequently raised is whether Asians need lower statin doses compared with Caucasians. Many practicing physicians believe that statin doses are lower in Asians because of the generally lower bodyweight and BMI. Whether this belief is based on sound scientific evidence needs to be reviewed. Furthermore, since the decision of optimal dose is based on both efficacy and safety, both of which may be impacted by genetic factors, one may ask whether pharmacogenetics plays a role in the dose difference, if such a difference exists. There is a clinical need to critically and comprehensively article the literature to answer these questions, and summarize future directions of research in the field. This article serves the above purpose.

Safety and efficacy of statins in Asians

Asian patients frequently have heightened responses to therapeutic drugs. As a consequence, the recommended drug doses are often lower in Asian countries than in Western countries. This practice extends to the use of cardiovascular drugs, including statins for the treatment of dyslipidemia. Pharmacokinetic investigations have noted higher plasma levels of statins in Asians compared with Caucasians, although postmarketing data for all statins have not identified any particular safety issues, even when statins are given at equivalent doses. The potential mechanisms of heightened response to statins in Asians are related to genetically based differences in the metabolism of statins at the level of hepatic enzymes and drug transporters. Studies indicate that lower statin doses achieve lipid improvements in Asian patients comparable with those observed with higher doses in Caucasians. In conclusion, prescribing lower starting doses of statins in Asians appears warranted while research on this subject continues.

Association between adherence to statin therapy and lipid control in Hong Kong Chinese patients at high risk of coronary heart disease

AIMS

To examine the pattern of adherence to statin therapy and to determine the association of adherence to statin therapy and the control of serum low-density lipoprotein (LDL)-cholesterol in a cohort of Hong Kong Chinese patients at high risk of coronary heart disease (CHD).

METHODS

This was a prospective observational cohort study conducted at the outpatient clinics of a public teaching hospital in Hong Kong. Patients at high risk of CHD who had been initiated on statin monotherapy for < 12 months were recruited. The statin prescription was dispensed in a bottle with the Medication Event Monitoring System (MEMS). Adherence was assessed in two dimensions: dose-count was defined as the percentage of doses taken, and dose-time was defined as the percentage of doses taken within the suggested time interval. Lipid profiles were obtained at baseline and during two follow-up visits at month 3 and month 6.

RESULTS

Eighty-three patients completed the study. The median adherence to dose-count and to dose-time were 95% (25-75th percentile = 87-99%) and 78% (25-75th percentile = 17-92%), respectively. Both dose-count and dose-time adherence declined slightly over the first 6 months of therapy. Living with family [relative risk (RR) = 0.79, 95% confidence interval (CI) 0.63, 0.91] and duration of therapy (RR = 0.99, 95% CI 0.98, 1.00) were negative predictors while number of family members (among those living with family) (RR = 1.05, 95% CI 1.00, 1.08) was a positive predictor for adherence to dose-count. Monthly household income (RR = 1.01, 95% CI 1.00, 1.02) and angina (RR = 1.29, 95% CI 1.05, 1.58) were positive predictors while living with family (RR = 0.74, 95% CI 0.55, 0.90) was a negative predictor for dose-time adherence. Percent reduction in serum LDL-cholesterol was correlated to dose-count (P < 0.001) and dose-time (P = 0.047) adherence. Statistically significant correlations were observed between adherence to dose-count and LDL reduction (R(2) = 0.130; P = 0.001), and between dose-time adherence and LDL reduction (R(2) = 0.048; P = 0.047).

CONCLUSION

High adherence to statin therapy was found in a cohort of Chinese patients at high risk of CHD and the adherence declined slightly over time. A weak association between adherence to statin dose-count and LDL reduction and a marginal association between dose-time adherence and LDL reduction were observed.

STATT: a titrate-to-goal study of simvastatin in Asian patients with coronary heart disease. Simvastatin Treats Asians to Target

BACKGROUND

Most published studies on the use of lipid-lowering agents to treat hypercholesterolemia have focused on Western populations, with few data on Asian populations.

OBJECTIVE

The Simvastatin Treats Asians to Target (STATT) study used a titrate-to-goal protocol to evaluate the efficacy and tolerability of simvastatin 20 to 80 mg/d in the treatment of Asian patients with coronary heart disease.

METHODS

This was a multicenter, open-label, uncontrolled, 14-week study in patients with coronary heart disease and serum low-density lipoprotein cholesterol (LDL-C) levels of 115-180 mg/dL and triglyceride levels of < or = 400 mg/dL. The dose of simvastatin was titrated from 20 to 80 mg/d to achieve the National Cholesterol Education Program (NCEP) LDL-C target of < or = 100 mg/dL. The primary efficacy measure was the percentage of patients achieving the NCEP target. Among secondary measures were the percentage of patients achieving European Society of Cardiology/European Atherosclerosis Society/European Society of Hypertension target LDL-C levels of < or = 115 mg/dL and the percentage change from baseline in lipid parameters. Tolerability was assessed in terms of the overall incidence of adverse experiences and the incidences of the most commonly reported adverse experiences.

RESULTS

The intent-to-treat analysis included 133 Asian patients (93 men, 40 women; mean age, 59.5 years), of whom 125 completed 14 weeks of therapy. Their mean blood pressure was 130.2/79.4 mm Hg. Overall, 104 (78.2%) patients treated with simvastatin achieved LDL-C levels < or = 100 mg/dL at week 14, and 125 (94.0%) achieved this target at some point during the study. Similarly, 122 (91.7%) patients achieved an LDL-C level < or = 115 mg/dL at week 14, and 130 (97.7%) achieved this target at some point during the study. Treatment with simvastatin had favorable effects on the lipid profile, producing significant percentage changes from baseline in all parameters (P < 0.001). Simvastatin was well tolerated across the dose range. Overall, 40 patients (30.1%) had > or = 1 clinical adverse experience. Only 14 (10.5%) had adverse experiences that were possibly, probably, or definitely related to study drug; none of these experiences were considered serious. The most common adverse experiences (> or = 3% incidence) were abdominal pain (6%); chest pain (5%); dizziness (4%); and asthenia/fatigue, fibromyalgia, headache, insomnia, and upper respiratory tract infection (3% each). No new or unexpected adverse experiences were seen at the higher doses.

CONCLUSIONS

Simvastatin was effective and well tolerated at doses of 20, 40, and 80 mg/d in Asian patients with coronary heart disease. Titration enabled the majority to achieve target LDL-C levels of < or = 100 mg/dL.

Effects of combination therapy with estrogen plus simvastatin on lipoprotein metabolism in postmenopausal women with type IIa hypercholesterolemia

We investigated the effects of estrogen and simvastatin, administered both alone and in combination, on the plasma lipid levels and lipoprotein-related enzymes in 45 postmenopausal women with type IIa hypercholesterolemia. They received 0.625 mg conjugated equine estrogen (n=15), 5 mg simvastatin (n=15), or the combination (n=15) daily for 3 months. We measured the concentrations of cholesterol and triglyceride in the plasma, and in the very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL)1 (1.019<d<1.045 g/ml) and LDL2 (1.045<d<1.063 g/ml), and high-density lipoprotein (HDL)2 (1.063<d<1.125 g/ml) and HDL3 (1.125<d<1.210 g/ml) subfractions, and apolipoproteins, and the activities of lipoprotein-metabolizing enzyme before and after treatment. All three treatments significantly lowered the plasma levels of total cholesterol, LDL1 cholesterol, and apolipoprotein B, C-II, and E. In combination therapy, significantly reduced levels of VLDL, IDL, and LDL2 cholesterol were also obtained. Combination therapy lowered total and LDL1 cholesterol significantly more than did estrogen alone. Estrogen and combination therapy significantly increased the levels of cholesterol in the HDL2 subfraction, triglyceride in the HDL2 and HDL3 subfractions, and apolipoprotein A-I and A-II. Estrogen treatment, but not combination therapy, also significantly raised the levels of total and IDL triglyceride. Estrogen and combined therapies significantly lowered the activities of hepatic triglyceride lipase and lecithin cholesterol acyltransferase. Findings indicate that combination therapy with estrogen plus simvastatin favorably affected lipid metabolism by reducing the concentrations of VLDL and IDL particles as well as large and small LDL particles, increasing the concentration of HDL particles, and preventing estrogen-induced increases in plasma triglyceride levels.

Sex-related differences in response of plasma lipids to simvastatin: the Saitama Postmenopausal Lipid Intervention Study. S-POLIS Group

The Saitama Postmenopausal Lipid Intervention Study was a multicenter, uncontrolled, collaborative study that investigated tolerability and sex-related differences in the response of serum lipids to simvastatin administered for 12 months in 122 postmenopausal women and 55 men with serum total cholesterol (TC) levels > or =220 mg/dL. With simvastatin treatment, TC and low-density lipoprotein cholesterol (LDL-C) levels decreased significantly at 1 month in both groups, and these decreased levels were maintained throughout treatment (P < 0.001). A significant decrease in triglyceride (TG) levels was also observed in both groups (P < 0.05). The mean percentage decreases in TC and LDL-C levels in women (20% and 28%, respectively) were significantly greater than those in men (15% and 20%, respectively) (P < 0.001). Mean percentage changes in TC and LDL-C levels in subgroups defined by stratification for baseline TC and LDL-C levels were also greater in women. There were no sex-related differences in the percentage changes in TG or high-density cholesterol levels, although the changes were influenced by baseline levels. Although the median dose of simvastatin (milligrams per kilogram of body weight) in women was significantly higher than in men (P < 0.001), the percentage changes in serum lipids were not correlated with the doses of simvastatin calibrated by body weight. Adverse reactions occurred in 8 men and 7 women, so there appeared to be no significant sex-related difference. Eleven patients had abnormal laboratory values. Simvastatin therapy for 12 months is well tolerated and effective for both women and men with hypercholesterolemia. Sex-related differences occurred in the response to simvastatin therapy of serum lipids, especially TC and LDL-C, with greater changes in lipid levels occurring in women.