• Prescription sequence analysis;
  • Flunarizine;
  • Anti-depressants;
  • Adverse drug reactions;
  • Prescription drugs;
  • Pharmacy records


Prescription sequence analysis (PSA) uses pharmacy-based prescription drug histories to detect a subset of drug effects: those that are themselves indications for changes in the prescribing of another drug. Dutch pharmacy practice ensures virtually complete drug histories. With a database of 25,000 patients, we used PSA to test an alleged link between the use of the anti-vertigo drug flunarizine and mental depression. The temporal sequence of anti-depressant use among flunarizine users shows no clustering that would suggest a causal link. PSA can be run within a few days, which may make it helpful in resolving certain of the periodic controversies about adverse drug reactions.