title: Enhanced cholesterol reduction by simvastatin in diltiazem-treated patients.
abstract: OBJECTIVE
  To investigate whether an interaction between diltiazem and the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor simvastatin may enhance the cholesterol-lowering response to simvastatin in diltiazem-treated patients.
  
  
  METHODS
  One hundred and thirty-five patients attending the Sheffield hypertension clinic who started consecutively on simvastatin for primary or secondary prevention of coronary heart disease (CHD) during the 2 years June, 1996-May 1998 were surveyed. From the clinic records we extracted and recorded absolute and percentage cholesterol responses to the starting dose of simvastatin and coprescription of diltiazem.
  
  
  RESULTS
  The cholesterol reduction for the 19 patients on diltiazem was 33.3% compared with 24.7% in the remaining 116 patients (median difference 8.6%, 95% CI 1.1-12.2%, P<0.02). The interindividual variability of cholesterol response to simvastatin was greater for patients not taking diltiazem than for those patients taking diltiazem. The ratio of the variances in response for the nondiltiazem group relative to the diltiazem group was 1.34 at 10 mg simvastatin daily (not significant, 95% CI 0.16-4.11), and 3.42 at 20 mg daily (P<0.01, 95% CI 1.26-7.18). Concurrent diltiazem therapy (P<0.04), age (P=0.001) and starting dose of simvastatin (P=0.002) were found to be significant independent predictors of percentage cholesterol response.
  
  
  CONCLUSIONS
  Patients who take both simvastatin and diltiazem may need lower doses of simvastatin to achieve the recommended reduction in cholesterol. The pharmacokinetic and pharmacodynamic aspects of this interaction need further study to confirm an enhanced effect on cholesterol reduction, and exclude an increased risk of adverse events.
authors.affiliation: University Section of Clinical Pharmacology and Therapeutics, Royal Hallamshire Hospital, Sheffield, UK. k.r.yeo@sheffield.ac.uk
authors.forename: K R
authors.initials: KR
authors.lastname: Yeo
authors.forename: W W
authors.initials: WW
authors.lastname: Yeo
authors.forename: E J
authors.initials: EJ
authors.lastname: Wallis
authors.forename: L E
authors.initials: LE
authors.lastname: Ramsay
mesh_terms: D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002784:Cholesterol / Q000097:blood*; D003625:Data Collection; D004110:Diltiazem / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D010352:Patient Dropouts; D019821:Simvastatin / Q000009:adverse effects / Q000494:pharmacology*
chemical_list: D000924:Anticholesteremic Agents; D002121:Calcium Channel Blockers; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D002784:Cholesterol; D019821:Simvastatin; D004110:Diltiazem