 The drugs studied were selected on the basis that the conditions treated had high incidence, prevalence and/or mortality, caused significant long-term morbidity and incurred high levels of expenditure and significant developments in prevention or treatment had been made in the last 10 years.The study noted considerable difficulties in cross border comparison of medication use.Sildenafil was reclassified in New Zealand in 2014 so it could be bought over the counter from a pharmacist.