The potential for drug interactions with statin therapy in Ireland.
BACKGROUND
Seven percent of acute hospital admissions result from adverse drug reactions, of which 25% are due to drug interactions. Adverse effects of statin drugs occur in 3% of patients, mainly due to co-prescribing with other lipid-lowering agents or agents that alter their metabolism.


OBJECTIVE
The aim of this study was to investigate co-prescribing of the frequently-used statin medications with interacting drugs.


METHODS
Data from the General Medical Services (GMS) scheme of the Eastern Health Board from January to December 1998 were used in this study. Using the coding index for statins, co-prescribing was identified when concomitant medications were administered under the same GMS claim number.


RESULTS
Of 7,602 patients prescribed statins, co-prescribing of simvastatin, atorvastatin and fluvastatin with competing substrates or inhibitors of their metabolism occurred in 32, 26 and 13.4% of prescriptions issued. Thirty-four per cent of patients on simvastatin, 28% on atorvastatin and 16% on fluvastatin were prescribed medications with drug interaction potential.


CONCLUSIONS
Co-prescribing of statins with competing substrates or inhibitors of their metabolism occurred in up to one-third of prescriptions issued. When statins are co-prescribed with recognised inhibitors of drug metabolism, pravastatin, which does not undergo significant hepatic metabolism, is the statin of choice.
Department of Pharmacology and Therapeutics, University of Dublin, Trinity College, Dublin, Ireland.
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Heerey
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Barry
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Ryan
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Kelly
D001189:Aryl Hydrocarbon Hydroxylases; D000069059:Atorvastatin; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D004347:Drug Interactions; D005229:Fatty Acids, Monounsaturated / Q000493:pharmacokinetics; D000077340:Fluvastatin; D006538:Heptanoic Acids / Q000493:pharmacokinetics; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000493:pharmacokinetics* / Q000627:therapeutic use; D007211:Indoles / Q000493:pharmacokinetics; D007494:Ireland; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D017035:Pravastatin / Q000493:pharmacokinetics; D011758:Pyrroles / Q000493:pharmacokinetics; D019821:Simvastatin / Q000493:pharmacokinetics; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors
D065607:Cytochrome P-450 Enzyme Inhibitors; D005229:Fatty Acids, Monounsaturated; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007211:Indoles; D011758:Pyrroles; D000077340:Fluvastatin; D000069059:Atorvastatin; D019821:Simvastatin; D006899:Mixed Function Oxygenases; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; D039181:Steroid 16-alpha-Hydroxylase; D017035:Pravastatin