Road traffic accident risk related to prescriptions of the hypnotics zopiclone, zolpidem, flunitrazepam and nitrazepam.
BACKGROUND
Despite the high prescription rate of benzodiazepine-like hypnotics (z-hypnotics), there is limited information on the road traffic accident risk associated with the use of these drugs. We wanted to investigate whether filling a prescription for zopiclone or zolpidem was associated with increased risk of road traffic accidents at a national population level. Nitrazepam and flunitrazepam were used as comparator drugs.


METHODS
All Norwegians 18-69 years (3.1 million) were followed-up from January 2004 until the end of September 2006. Information on prescriptions, road traffic accidents and emigration/death was obtained from three Norwegian population-based registries. The first week after the hypnotics had been dispensed was considered to be the exposure period. Standardized incidence ratios (SIRs) were calculated by comparing the incidence of accidents in the exposed person-time to the incidence of accidents in the unexposed person-time.


RESULTS
During exposure, 129 accidents were registered for zopiclone, 21 for zolpidem, 27 for nitrazepam and 18 for flunitrazepam. The SIRs were (SIR for all ages and both sexes combined; 95% CI): z-hypnotics (zopiclone+zolpidem) 2.3; 2.0-2.7, nitrazepam 2.7; 1.8-3.9 and flunitrazepam 4.0; 2.4-6.4. The highest SIRs were found among the youngest users for all hypnotics.


CONCLUSIONS
This study found that users of hypnotics had a clearly increased risk of road traffic accidents. The SIR for flunitrazepam was particularly high.
Gustavsen
Ingebjørg
I
Division of Forensic Toxicology and Drug Abuse, Norwegian Institute of Public Health, Oslo, Norway. ingebjorg.g.gustavsen@fhi.no
Bramness
Jørgen G
JG
Skurtveit
Svetlana
S
Engeland
Anders
A
Neutel
Ineke
I
Mørland
Jørg
J
D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000293:Adolescent; D000328:Adult; D000368:Aged; D053961:Azabicyclo Compounds / Q000009:adverse effects*; D005260:Female; D005445:Flunitrazepam / Q000009:adverse effects*; D005500:Follow-Up Studies; D006801:Humans; D006993:Hypnotics and Sedatives / Q000009:adverse effects*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009567:Nitrazepam / Q000009:adverse effects*; D009664:Norway / Q000453:epidemiology; D010879:Piperazines / Q000009:adverse effects*; D011725:Pyridines / Q000009:adverse effects*; D012307:Risk Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000188:drug therapy*; D055815:Young Adult; D000077334:Zolpidem
D053961:Azabicyclo Compounds; D006993:Hypnotics and Sedatives; D010879:Piperazines; D011725:Pyridines; C515050:zopiclone; D005445:Flunitrazepam; D000077334:Zolpidem; D009567:Nitrazepam