Even though the relationship between antiarrhythmic drug usage and subsequent prostate cancer (PCa) risk has recently been highlighted, relevant findings in the previous literature are still inconsistent. In addition, very few studies have attempted to investigate the association between sodium channel blockers or potassium channel blockers for arrhythmia and the subsequent PCa risk. Therefore, this cohort study aimed to find the relationship between antiarrhythmic drug usage and the subsequent PCa risk using a population-based dataset. The data used in this study were derived from the Longitudinal Health Insurance Database 2005, Taiwan, China. We respectively identified 9988 sodium channel blocker users, 3663 potassium channel blocker users, 65 966 beta-blocker users, 23 366 calcium channel blockers users, and 7031 digoxin users as the study cohorts. The matched comparison cohorts (one comparison subject for each antiarrhythmic drug user) were selected from the same dataset. Each patient was tracked for a 5-year period to define those who were subsequently diagnosed with PCa. After adjusting for sociodemographic characteristics, comorbidities, and age, Cox proportional hazard regressions found that the hazard ratio (HR) of subsequent PCa for sodium channel blocker users was 1.12 (95% confidence interval [CI]: 0.84-1.50), for potassium channel blocker users was 0.89 (95% CI: 0.59-1.34), for beta-blocker users was 1.08 (95% CI: 0.96-1.22), for calcium channel blocker users was 1.14 (95% CI: 0.95-1.36), and for digoxin users was 0.89 (95% CI: 0.67-1.18), compared to their matched nonusers. We concluded that there were no statistical associations between different types of antiarrhythmic drug usage and subsequent PCa risk.
Adrenergic beta-Antagonists/adverse effects* ; Adult ; Age Factors ; Aged ; Anti-Arrhythmia Agents/adverse effects* ; Calcium Channel Blockers/adverse effects* ; Cohort Studies ; Comorbidity ; Databases, Factual ; Digoxin/adverse effects* ; Humans ; Incidence ; Male ; Middle Aged ; Potassium Channel Blockers/adverse effects* ; Prostatic Neoplasms/epidemiology* ; Retrospective Studies ; Socioeconomic Factors ; Sodium Channel Blockers/adverse effects* ; Taiwan/epidemiology*

Drug-drug interaction (DDI) is defined as a change in effect or safety of a drug by another co-administered drug. The fact that more than half of the market withdrawal cases for the past ten years was caused by potentially fatal DDI's demonstrates its clinical importance. The mechanism of DDI can be categorized into pharmacokinetic and pharmacodynamic interactions. Most of the clinically important drug interactions are caused by inhibition or induction of oxidative metabolism by cytochrome P450 (CYP) isozymes. Recent researches are also focusing on drug transporter interactions as another significant factor underlying DDI's. It is hard to prevent unexpected or rare DDI's. However, most of the cases of DDI occur from an erroneous prescription of drugs that are already known to result in deleterious interactions. To avoid such well-established DDI's, physicians are first recommended to utilize hands-on summary tables for CYP substrates before prescribing. It should also be remembered that old age, polypharmacy and damaged hepatic or renal function are risk factors of DDI as well as adverse drug reactions. Moreover, patients treated with drugs with a narrow therapeutic index (immunosuppressants, antiarrhythmics, anticoagulants, digoxin, theophylline etc) deserve a special consideration when their prescriptions are changed. In Korea, the clinical significance of DDI has been underemphasized. The fundamental prescription to this old prescription habit is to teach medical students and physicians clinical pharmacology and therapeutics, which have long been neglected in Korea.
Anticoagulants ; Cytochrome P-450 Enzyme System ; Digoxin ; Drug Interactions ; Drug-Related Side Effects and Adverse Reactions ; Humans ; Isoenzymes ; Korea ; Metabolism ; Pharmacology, Clinical ; Polypharmacy ; Prescriptions ; Product Recalls and Withdrawals ; Risk Factors ; Students, Medical ; Theophylline