The effect of introducing rebate contracts to promote generic drug substitution, on doctors' prescribing practices

As of 1 April 2007, pharmacists in Germany filling prescriptions covered by the statutory health insurance system (Gesetzliche Krankenversicherung, GKV) are required, whenever possible, to dispense a preparation that contains the same active substance and for which a rebate contract is in effect. The physician can block drug substitution by crossing out "aut idem" ("or the like") on the prescription form. The latter option has existed since 2002. We studied the possible effect of the introduction of rebate contracts on the use of the no-substitution option.

Three independent random samples were taken from the routine data of the Gmünder ErsatzKasse (GEK, a statutory health insurance carrier). The samples consisted of 0.5% of the insured adult population in the month of October in the years 2006, 2007, and 2008 (n = 6195; n = 6300; n = 6845). Within these sample groups, all medication orders in which the physician could potentially have exercised a no-substitution option were selected, and the corresponding prescriptions were examined.

The percentage of no-substitution prescriptions rose from October 2006 to October 2007, and then rose still further to October 2008 (14.4%, 18.4%, 19.0%; p for trend < 0.0001). Considerable differences were seen between physicians belonging to different regional Associations of Statutory Health Insurance Physicians (Kassenärztliche Vereinigungen). In about one-quarter of the no-substitution prescriptions for 2007 and 2008 (25.1%, 25.7%), the prescribed medication was itself included in a rebate contract.

The use of the no-substitution option is not uniform across Germany at present. Rebate contracts and the no-substitution option require further evaluation. Moreover, the dispensing of medications urgently needs a more stable regulatory framework.