Pharmaco-economic assessment of the HMG-CoA reductase inhibitors.

Walters L.

Department of Pharmacology, University of Cape Town.

OBJECTIVE. To perform a comparative pharmaco-economic assessment of two HMG-CoA reductase inhibitors. DESIGN. A cost-effectiveness analysis was employed using comparative efficacy data from selected clinical trials. A comprehensive international literature search formed the basis for this selection. Criteria for inclusion of clinical trial results in the analysis were set a priori. Acquisition costs used were the recommended reimbursement prices as at September 1994. MAIN OUTCOME MEASURES. Two outcome measures are reported: (i) the comparative cost-effectiveness in lowering blood lipid concentrations; and (ii) the comparative cost-effectiveness of the medicines when used to achieve a predetermined therapeutic goal. RESULTS. The average cost per 1% decrease in total cholesterol is 21.9% higher on 10 mg pravastatin daily than on 10 mg simvastatin daily. Similarly the average cost per 1% decrease in low-density lipoprotein (LDL) cholesterol is 23.1% higher on 10 mg pravastatin than on 10 mg simvastatin daily. This difference is consistent throughout the dosage range. The use of incremental doses of simvastatin monotherapy in order to reach a predetermined therapeutic goal (LDL < or = 4.14 mmol/l) is more cost-effective than an equivalent pravastatin dosage regimen. Total treatment costs for simvastatin-treated patients are 3.5% less than for pravastatin-treated patients. More patients on simvastatin are successfully treated; the difference in overall treatment costs per successfully treated patient is 27.9% in favour of simvastatin. Sensitivity analysis shows these results to be stable under extreme scenarios. CONCLUSIONS. This analysis employed objective comparative efficacy data obtained from peer-reviewed sources to compare the economic and clinical outcomes of simvastatin and pravastatin in the treatment of hypercholesterolaemia. The acquisition cost of simvastatin is 10.3-22.8% higher than an equivalent milligram dose of pravastatin, depending on the dosage used. However, because of the greater milligram potency of simvastatin, it is a more cost-effective alternative. Simvastatin therefore provides better value for money than pravastatin in lowering lipid levels in clinical practice.

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The sensitivity of leukemic bone marrow to simvastatin is lost at remission: a potential purging agent for autologous bone marrow transplantation.

Millar JL.

Section of Academic Haematology, Sutton, Surrey, England.

BACKGROUND: Autologous bone marrow transplantation (ABMT) is frequently used in the treatment of malignant disease but carries the risk of reintroducing tumor cells into the patient. Methods are required for removing malignant cells from harvested bone marrow (BM) without impairing hematopoietic reconstitution. We have shown that simvastatin is toxic to leukemic progenitor cells at a concentration that conserves normal BM progenitors and may be of use clinically as a novel BM purging agent. METHODS: A two-stage culture system was used to compare the effects of simvastatin on both normal BM progenitor and primary acute myeloid leukemia (AML) cells. AML cells and normal BM mononuclear cells were incubated for 18 hours in suspension culture with 10 micrograms per mL simvastatin and the numbers of surviving clonogenic progenitor cells assayed in semisolid agar culture. RESULTS: Following simvastatin treatment of 18 AML cell populations, the mean surviving fraction of progenitor cells was 21.3 +/- 4.8% ( +/- standard error of the mean [SEM]). In contrast, the mean survival of normal BM progenitors from 16 donors was 89.6 +/- 8.6% ( +/- SEM). Samples were taken from 6 AML patients before treatment and after remission of disease had been induced by chemotherapy. In 5 of these cases the AML sample was significantly more sensitive to simvastatin than the remission sample, 4 of the 5 showed > 80% difference in progenitor cell survival. CONCLUSIONS: AML progenitor cells are sensitive to a short-term exposure to simvastatin that spares normal BM hematopoietic progenitor cells. We conclude that simvastatin may be an effective in vitro purging agent in ABMT for AML.

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Development and progression of atherosclerosis in aorta from heterozygous and homozygous WHHL rabbits. Effects of simvastatin treatment.

Reid JL.

Department of Medicine and Therapeutics, Western Infirmary, Glasgow, UK.

This study was conducted to define progression of atherosclerosis in both homozygous and heterozygous Watanabe heritable hyperlipidemic (WHHL) rabbits and to investigate the ability of the HMG CoA reductase inhibitor simvastatin to attenuate progression of the disease. We examined contractile responses to phenylephrine and endothelium-dependent relaxation in response to carbachol in thoracic aorta at 3, 6, 9, and 12 months in control New Zealand White (NZW) rabbits, homozygous WHHL rabbits, and heterozygous WHHL rabbits. Homozygous and heterozygous rabbits were treated with simvastatin (10 mg/kg per day) from 3 to 6 months and from 9 to 12 months of age. Simvastatin significantly reduced serum cholesterol levels in young heterozygotes, with a nonsignificant trend toward a reduction in older heterozygotes. In homozygotes, no significant fall was observed. Contractile function declined progressively with age in all groups--most in homozygotes and least in NZW rabbits. Relaxation was unaffected by age in NZW rabbits; relaxation declined in the heterozygotes and declined to a greater extent in homozygotes. Simvastatin retarded the loss of function in the young heterozygotes. Similar trends were observed in young homozygotes and older heterozygotes, with no effect in older homozygotes. Histological studies revealed the progressive development of early atherosclerosis in heterozygotes, and more advanced atherosclerosis was observed in homozygotes. Simvastatin did not inhibit development of atheroma. A correlation was observed between vascular function and structure. However, functional changes preceded the development of atheroma. In addition, we have demonstrated that simvastatin can help to reduce the loss of vascular function associated with the progression of atherosclerosis in the heterozygous WHHL rabbit.

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Effects of simvastatin and pravastatin on endothelium-dependent relaxation in hypercholesterolemic rabbits.

Metze K.

Department of Experimental Medicine/University of Campinas, Sao Paulo, Brazil.

OBJECTIVES: The present study was conducted to investigate endothelium-dependent relaxation in hypercholesterolemic rabbits after treatment with two HMG-CoA reductase inhibitors: Simvastatin and Pravastatin. METHODS: Thirty male New Zealand rabbits were randomly assigned to Control, Simvastatin and Pravastatin groups and fed a diet supplemented with lipids and cholesterol (coconut oil 10% and cholesterol 1%) for 8 weeks. The drugs were administered in dosages of 10 mg/kg from the fourth to seventh weeks; at the end of the seventh week, plasma cholesterol was determined, and the Pravastatin dosage adjusted to 15 mg/kg to obtain similar levels of plasma cholesterol for the two experimental groups. At the end of the 8th week, the animals were killed and aorta removed for histologic examination and the measurement of cholesterol content, as well as for the conduction of endothelium-dependent relaxation studies. RESULTS: At the end of the study serum cholesterol was reduced by 57.1% in the Pravastatin group and 58.4% in the Simvastatin group, with the aortic cholesterol content in the former being significantly lower than that of the Simvastatin and Control groups (p < 0.05). Histologic examination also revealed a significant decrease in volume fractions of foam cells in Pravastatin-treated animals, whereas endothelium-dependent relaxation in response to ACh was significantly impaired in the Simvastatin group. No significant difference was found in relaxation induced by nitroprusside. CONCLUSIONS: In spite of the similar reduction in plasma cholesterol obtained by different doses, it seems that Pravastatin preserves the endothelium-dependent relaxation of aortic rings of hypercholesterolemic rabbits more effectively than does Simvastatin.

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Simvastatin inhibits the cellular signaling and proliferative action of arginine vasopressin in cultured rat glomerular mesangial cells.

Saito T.

Department of Medicine, Jichi Medical School, Tochigi, Japan.

The present study was undertaken to determine whether an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, simvastatin, modulates the cellular action of arginine vasopressin (AVP) in the cultured rat glomerular mesangial cells. AVP increases cellular free calcium ([Ca2+]i) in a dose-dependent manner. The 1 x 10(-7) M AVP-mobilized [Ca2+]i was significantly reduced in the cells pretreated with 1 x 10(-6) M simvastatin. AVP produced a biphasic change in cellular pH, namely, an early acidification followed by a sustained alkalinization, and the AVP-induced cellular alkalinization disappeared after exposing to simvastatin. 1 x 10(-7) M AVP activated mitogen-activated protein (MAP) kinase from 15.5-30.4 pmol/mg protein, an effect significantly less in the presence of simvastatin. Also, 1 x 10(-7) M AVP significantly increased [3H]thymidine incorporation by 1.6-fold, and its incorporation was totally diminished in cells pretreated with simvastatin. The AVP-induced [Ca2+]i mobilization and MAP kinase activation were totally restored when cells were preexposed to a mixture of mevalonate and simvastatin. [3H]AVP receptor binding was not affected by the simvastatin treatment. 1 x 10(-7) AVP increased inositol trisphosphate production by 1.8-fold, which was significantly reduced by the presence of simvastatin. These results may indicate that nonsterol pathway plays a crucial role in the cellular action of AVP to produce cell growth of glomerular mesangium.

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Effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in ischemic rat hearts.

Ichihara K.

Department of Pharmacology, Hokkaido College of Pharmacy, Otaru, Japan.

The aim of the present study was to examine the effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors on mitochondrial respiration in ischemic rat hearts, and to compare the effects between water-soluble pravastatin and lipid-soluble simvastatin. Either vehicle (0.5% carboxymethyl cellulose), pravastatin (2 or 4 mg/kg per day), or simvastatin (1 or 2 mg/kg per day) was orally administered for 3 weeks. Ischemia was induced by ligating the aorta for 60 min in anesthetized open chest rats under artificial respiration. The hearts were removed, mitochondria were isolated, and the respiration was determined by polarography using glutamate and succinate as substrates. When succinate was used as a substrate, the ADP-stimulated respiration (QO3) and ATP production per unit oxygen (ADP/O ratio) were decreased by ischemia. The decreases in QO3 and ADP/O ratio in the pravastatin- and simvastatin-treated groups appeared to be more prominent than those in the vehicle-treated group. This was especially true in the simvastatin-treated group. The ADP-limited respiration (QO4) with succinate in the vehicle-treated heart was slightly increased by ischemia, while that in the pravastatin- or simvastatin-treated hearts was decreased. In conclusion, HMG-CoA reductase inhibitors may result in worsening of myocardial mitochondrial respiration during ischemia.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7796866&dopt=Abstract simvastatin, Zocor