A double-blind, randomized study evaluated the interaction between an antiaggregating agent with vitamin E in 100 patients at risk for transient ischemic attacks (TIAs) (Steiner et al. 1995). Patients were administered either aspirin (325 mg) or aspirin plus vitamin E (400 IU/day) for two years. The group receiving combination therapy had a significant reduction in ischemic events and platelet adhesiveness. However, the incidence of hemorrhagic stroke was not affected by treatment. The combination of vitamin E and aspirin appears to be safe and may benefit patients at risk for TIAs.

Vitamin E inhibits drug uptake in a dose-dependent manner in human cultured fibroblasts exposed to single and repetitive doses of chloroquine and other cationic amphiphilic drugs (Scuntaro et al. 1996). Cationic amphiphilic drugs encompass a variety of therapeutic classes of medications including antiarrhythmics, antidepressants, and neuroleptics.

Vitamin E inhibits drug uptake in a dose-dependent manner in human cultured fibroblasts exposed to single and repetitive doses of chlorpromazine and other cationic amphiphilic drugs (Scuntaro et al. 1996). Cationic amphiphilic drugs encompass a variety of therapeutic classes of medications including antiarrhythmics, antidepressants, and neuroleptics.

A study with ten healthy subjects evaluated the interaction between water-soluble vitamin E and cyclosporine (Chang et al. 1996). After two doses of cyclosporine (10 mg/kg po), oral vitamin E was randomly administered with the drug. Concomitant administration of vitamin E and cyclosporine significantly decreased the clearance and steady-state volume of distribution for the drug. The combination therapy increased the area under the curve (AUC) for cyclosporine. The increased AUC may be the result of enhanced bioavailability. However, a subsequent in vitro study suggested that vitamin E and cyclosporine antagonize one another (Van Rensburg et al. 1998).

Vitamin E inhibits drug uptake in a dose-dependent manner in human cultured fibroblasts exposed to single and repetitive doses of desipramine and other cationic amphiphilic drugs (Scuntaro et al. 1996). Cationic amphiphilic drugs encompass a variety of therapeutic classes of medications including antiarrhythmics, antidepressants, and neuroleptics.

Preliminary findings indicate that hormone replacement therapy (HRT) may preserve the content of vitamin E in LDL particles that, in turn, reduce the amount of oxidized LDL (Clemente et al. 1996). Concomitant administration of vitamin E with transdermal estradiol was shown to improve LDL, HDL, and total cholesterol status in postmenopausal women (Inal et al. 1997). Most studies showing a benefit from vitamin E on heart disease risk have used quantities of vitamin E (400 to 800 IU/day) that are much higher than RDA values (Emmert and Kircher 1999).

There are conflicting reports regarding the effect of gemfibrozil on vitamin E status in hyperlipidemic patients. In one study, gemfibrozil treatment in men with combined hyperlipidemia reduced serum ubiquinone-10 and gamma- and alpha-tocopherol levels (Aberg et al. 1998). In another study, gemfibrozil had no effect on vitamin E status and increased the LDL vitamin E/lipid peroxide ratio concentrations (Yoshida et al. 1998).

HMG-CoA reductase therapy may decrease the antioxidant capacity of vitamin E on LDL cholesterol (Palomaki et al. 1998). However, coadministration of vitamin E (300 IU) with simvastatin (20 mg) improved markers of blood vessel elasticity in hypercholesterolemic patients more than simvastatin monotherapy (Neunteufl et al. 1998). Similar benefits may be observed with fluvastatin and other HMG-CoA reductase inhibitors.

Oral contraceptives reduce some of the vitamins and enzymes involved in the oxidative defense system (Ciavatti and Renaud 1991; Tangney and Driskell 1978). Impaired antioxidant status can increase the susceptibility to lipid peroxidation and possibly thrombosis in women (Ciavatti and Renaud 1991). Some of these effects can be counteracted by vitamin E supplements.

Vitamin E inhibits drug uptake in a dose-dependent manner in human cultured fibroblasts exposed to single and repetitive doses of propranolol and other cationic amphiphilic drugs (Scuntaro et al. 1996). Cationic amphiphilic drugs encompass a variety of therapeutic classes of medications including antiarrhythmics, antidepressants, and neuroleptics.

An in vitro study suggested that vitamin E antagonized the chemosensitizing effects of verapamil (Van Rensburg et al. 1998). Tests performed using the human small cell lung cancer line demonstrated that the inclusion of alpha-tocopherol (25 mcg/mL) prevented the ability of verapamil (2 mcg/mL) to sensitize the cells to the effects of doxorubicin and vinblastine.

Vitamin E does not appear to enhance the pharmacologic effects of warfarin (Kim and White 1996). However, the administration of high doses of vitamin E to individuals with reduced levels of vitamin K may potentiate a vitamin K deficiency and increase the anticoagulant effect of warfarin (Corrigan 1982). Although the mechanism of this interaction is unclear, vitamin E may affect the carboxylation of prothrombin, a vitamin-K-dependent step in the production of coagulation factors.

Antiviral activity and bone marrow toxicity of zidovudine (AZT) were evaluated in the presence of water-soluble vitamin E (alpha-D-tocopherol acid succinate (ATS)) in two cell test systems (Gogu et al. 1989). In the MT4 cell line, ATS displayed a dose-dependent increase in anti-HIV activity that was six times greater than when AZT was also administered. In addition, vitamin E showed significant protection against AZT-induced toxicity in murine bone marrow cells.

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Chang T, Benet LZ, Hebert MF. The effect of water-soluble vitamin E on cyclosporine pharmacokinetics in healthy volunteers. Clin Pharm & Ther. 1996;59(3):297-303.

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Clemente C, Caruso MG, Berloco P, Buonsante A, Giannandrea B, Di Leo A. Alpha-tocopherol and beta-carotene serum levels in post-menopausal women treated with transdermal estradiol and oral medroxyprogesterone acetate. Horm Metab Res. 1996;28(10):558-561.

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Emmert DH, Kircher JT. The role of vitamin E in the prevention of heart disease. Arch Fam Med. 1999;8(6):537-542.

Gogu S, Beckman B, Rangan S, et al. Increased therapeutic efficacy of zidovudine in combination with vitamin E. Biochem Biophys Res Commun. 1989; 165:401-407.

Inal M, Sunal E, Kanbak G, Zeytinoglu S. Effects of postmenopausal hormone replacement therapy and alpha-tocopherol on the lipid profiles and antioxidant status. Clin Chim Acta. 1997;268(1-2):21-29.

Kim JM, White RH. Effect of vitamin E on the anticoagulant response to warfarin. Am J Cardiol. 1996;77(7):545-546.

Neunteufl T, Kostner K, Katzenschlager R, et al. Additional benefit of vitamin E supplementation to simvastatin therapy on vasoreactivity of the brachial artery of hypercholesterolemic men. J Am Coll Cardiol. 1998;32(3):711-716.

Palomaki A, Malminiemi K, Solakivi T, Malminiemi O. Ubiquinone supplementation during lovastatin treatment: effect on LDL oxidation ex vivo. J Lipid Res. 1998;39(7):1430-1437.

Scuntaro I, Kientsch U, Wiesmann U, et al. Inhibition by vitamin E of drug accumulation and of phospholipidosis induced by desipramine and other cationic amphiphilic drugs in human cultured cells. Br J Pharmacol. 1996;119:829-834.

Steiner M, Glantz M, Lekos A. Vitamin E plus aspirin compared with aspirin alone in patients with transient ischemic attacks. Am J Clin Nutr. 1995;62(suppl):1381S-4138S.

Tangney CC, Driskell JA. Vitamin E status of young women on combined-type oral contraceptives. Contraception. 1978;17(6):499-512.

Van Rensburg CE, Jooné G, Anderson R. Alpha-tocopherol antagonizes the multidrug-resistance-reversal activity of cyclosporin A, verapamil, GF120918, clofazimine and B669. Cancer Lett. 1998;127(1-2):107-112.

Yoshida H, Ishikawa T, Ayaori M, et al. Beneficial effect of gemfibrozil on the chemical composition and oxidative susceptibility of low density lipoprotein: a randomized, double-blind, placebo-controlled study. Atherscl. 1998;139(1):179-187.