Drug Interactions between aspirin / omeprazole and Vita-Plus E Natural

MONITOR: Vitamin E may potentiate the effects of anticoagulants and platelet inhibitors. Vitamin E is thought to inhibit the oxidation of reduced vitamin K and interfere with the functions of vitamin K-dependent clotting factors. These effects appear to be dose-dependent and greater in individuals with preexisting vitamin K deficiency. In one study, administration of vitamin E 42 units/day for one month increased the hypoprothrombinemic effect of a single dose of dicumarol in 3 healthy volunteers, as demonstrated by a decrease in prothrombin activity from 52% to 33% thirty-six hours postdose. The interaction was also suspected in a patient who developed ecchymoses and hematuria following two months of vitamin E supplementation at a dosage of 800 to 1200 units/day while taking warfarin. In contrast, two studies found no significant effect of vitamin E on the hypoprothrombinemic effect of chronic warfarin therapy when administered at relatively high dosages (800 or 1200 units/day) to 21 subjects for one month or at low dosages (100 or 400 units/day) to 12 subjects for four weeks. With respect to antiplatelet activities, data from in vitro and ex vivo human studies suggest that vitamin E can inhibit collagen-induced platelet activation and protein kinase C-dependent platelet aggregation. Clinically significant antiplatelet effects have not been consistently observed in published studies, particularly at dosages below 400 units/day. However, there have been isolated reports of excessive bleeding in surgical patients who had taken vitamin E regularly prior to surgery, and one controlled clinical trial found that supplementation with only 50 mg/day of vitamin E resulted in an increase in subarachnoid hemorrhage in male smokers aged 55 to 74 years (n=409). In a random sampling of that same population of male smokers, gingival bleeding was also more common in subjects who received vitamin E with aspirin compared to those who received either agent alone or neither.

MANAGEMENT: Patients should consult a healthcare provider before taking any nutritional supplements like vitamin E. Close clinical and laboratory observation for hematologic complications may be appropriate when vitamin E supplementation at dosages greater than 400 units/day is initiated in patients stabilized on anticoagulant or antiplatelet therapy. The dose of the anticoagulant or antiplatelet drug may require adjustment during and after treatment with vitamin E. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools.

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Coadministration with proton pump inhibitors may decrease the oral bioavailability of aspirin and other salicylates. The interaction has been studied with omeprazole and aspirin, although data are conflicting. In one study, pretreatment with omeprazole (20 mg/day for 2 days) in 11 healthy volunteers led to a significant and progressively greater reduction in the mean serum salicylate level at 30, 60, and 90 minutes after administration of aspirin (650 mg single dose). The investigators suggest that acid suppression may reduce the lipophilic nature of aspirin, thereby adversely affecting its absorption from the gastrointestinal tract. Another study found no effect of omeprazole pretreatment (20 mg/day for 4 days) on plasma salicylate and aspirin levels, skin bleeding times, or antiplatelet effect of low-dose aspirin (125 mg single dose) in 14 healthy volunteers. However, these results do not exclude the possibility that omeprazole might interfere with the analgesic, antipyretic, or anti-inflammatory effects of aspirin, which has been demonstrated in rats.

Proton pump inhibitors may enhance the release rate of salicylates from enteric-coated formulations due to premature disruption of the coating and intragastric release of the drug secondary to an increase in gastric pH. In eight healthy volunteers, omeprazole pretreatment (20 mg/day for 4 days) did not affect the bioavailability of salicylate from uncoated aspirin tablets but significantly increased the absorption rate of salicylate from enteric-coated sodium salicylate tablets. The clinical significance of this interaction is unknown. Theoretically, it may increase the risk of gastric adverse effects associated with salicylates.

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