Table 2 Criteria used for assessing causality of suspected medication-related problems (based on Howard et al18)

1	Known adverse drug reaction, toxic reaction, response to omission of therapy or inadequate therapy
2	Reasonable temporal relationship between commencement or cessation/omission of therapy and onset of problem
3	Risk of further problems likely to be reduced by dose reduction or increase, discontinuation, closer monitoring or commencement of therapy
4	Not explained by any other known condition of predisposition to the patient, or This condition/predisposition is likely to be exacerbated by the presence/absence of the drug
5	For drug toxicity:
	Symptoms reappeared upon re-exposure
	Laboratory tests showed toxic drug levels or drug-induced metabolic disturbances that explained the symptom
	Symptoms resolved on dose reduction or discontinuation of the drug
	For drug omission:
	Symptoms resolved upon re-introduction of the drug or dose increase

If five criteria fulfilled, then definite. If four criteria fulfilled, then probable. If three criteria fulfilled, then possible. If two or fewer criteria fulfilled, then either not drug-related or unevaluable.