Prescription of QT-prolonging drugs in a cohort of about 5 million outpatients.
Many drugs prolong the QT interval and increase the risk of torsade de pointes. Concurrent use of two or more of these drugs can further increase the risk, but the prevalence of concurrent prescription of QT-prolonging drugs is not known. Using the administrative claims database of a national pharmaceutical benefit manager, we conducted a retrospective cohort study in 4,825,345 subjects aged 18 years or older. After identifying 50 drugs with QT-prolonging potential, and an additional 26 drugs that inhibit the metabolic clearance of QT-prolonging drugs, we measured the frequency of overlapping prescriptions for two or more of these drugs in the outpatient setting in 1999. Nearly 1.1 million subjects (22.8%) filled 4.4 million prescriptions for QT-prolonging drugs. Of these, 103,119 subjects (9.4%) filled overlapping prescriptions for two or more of the drugs or for a QT-prolonging drug and another drug that inhibits its clearance; 7249 subjects (0.7%) filled overlapping prescriptions for three or more of these drugs. Twenty-two percent of subjects who filled overlapping prescriptions were aged 65 or older; 74% were women. Antidepressants were involved in nearly 50% of the cases. Concurrent prescription of QT-prolonging drugs is common in the outpatient setting, and antidepressants are involved in half of these cases. Large pharmaceutical claims databases are useful for detecting potentially harmful prescribing behaviors, but better clinical evidence on medication safety is needed before such a system can be implemented fully.
Curtis
Lesley H
LH
Center for Clinical and Genetic Economics, Duke University Medical Center, Durham, North Carolina 27510, USA.
Østbye
Truls
T
Sendersky
Veronica
V
Hutchison
Steve
S
Allen LaPointe
Nancy M
NM
Al-Khatib
Sana M
SM
Usdin Yasuda
Sally
S
Dans
Peter E
PE
Wright
Alan
A
Califf
Robert M
RM
Woosley
Raymond L
RL
Schulman
Kevin A
KA
D000328:Adult; D000368:Aged; D000639:Amitriptyline / Q000009:adverse effects; D000900:Anti-Bacterial Agents / Q000009:adverse effects; D000890:Anti-Infective Agents / Q000009:adverse effects; D018687:Antidepressive Agents, Second-Generation / Q000009:adverse effects; D000929:Antidepressive Agents, Tricyclic / Q000009:adverse effects; D017291:Clarithromycin / Q000009:adverse effects; D015331:Cohort Studies; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D004357:Drug Synergism; D004917:Erythromycin / Q000009:adverse effects; D005260:Female; D005473:Fluoxetine / Q000009:adverse effects; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015242:Ofloxacin / Q000009:adverse effects; D010045:Outpatients; D019338:Polypharmacy; D016171:Torsades de Pointes / Q000139:chemically induced*; D014481:United States
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D018687:Antidepressive Agents, Second-Generation; D000929:Antidepressive Agents, Tricyclic; D005473:Fluoxetine; D000639:Amitriptyline; D004917:Erythromycin; D015242:Ofloxacin; D017291:Clarithromycin