Background Hospitals cannot include all marketed drugs in their formularies. Those drugs not included in the formulary (NFD) need an alternative drug available (ALT) in order to cover all patient requirements.

Purpose To assess the prevalence of NFD prescriptions and factors associated with the acceptance recommendation on an ALT.

Material and methods Retrospective study performed in a tertiary university hospital from 2012 to 2015.

Data collected: drug-related problems (DRP); DRP-related NFD prescription (DRP-NFD); admissions; and admissions with prescription of NFD. NFD classification: NFD with ALT (NFD-ALT) (drug able to present the same clinical effect and safety profile than NFD); non-replaceable NFD (NFD-NR) (drug for which no therapeutic alternative is available); or NFD of doubtful therapeutic efficacy (NFD-DTE) (drug with limited evidence on its effectiveness).

Clinical pharmacists made an annotation in the electronic medical record, offering an ALT when it was available, proceeding to its acquisition when it was NFD-NR and recommending withdrawal when it was NFD-DTE.

Admissions data collected: demographic; Charlson comorbidity index; urgent/scheduled admission; surgical/medical service; number of concomitant drugs; and ATC-group. Acceptance of ALT recommendation was evaluated.

Results Total admissions: 69,686; DRP: 10,480; admissions affected by DRP-NFD: 441 (0.6%). DRP-NFD: 557 (5.1%), where: NFD-ALT: 496 (89%); NFD-NR: 5 (0.9%); NFD-DTE: 56 (10.1%).

Most commonly involved ATC groups: urological preparations (G04):71 (16.1%); renin-angiotensin system (C09): 47 (10.7%); agents against obstructive airway diseases (R03): 47 (10.7%); ophthalmologic (S01): 43 (9.8%); hypolipidaemic (C10): 25 (5.7%); systemic antihistamines (R06): 20 (4.5%); systemic corticosteroids (H02): 17 (3.9%); diuretics (C03): 16 (3.6%); laxatives (A06): 12 (2.7%); anti-inflammatory/antirheumatic (M01): 11 (2.5%); others: 132 (29.9%).

From 496 NFD-ALT, 154 (31%) recommended ALT were accepted, 287 (57.9%) not accepted and 55 (11.1%) were non-evaluable.

Conclusion Most drugs not included in the formulary are substitutable for an available alternative (99.1%).

Although no factors are significantly associated, there is a trend towards acceptance of the recommended therapeutic alternative in patients with prescription of a higher number of concomitant drugs.

Acceptance was less than 30% when the ATC involved were systemic antihistamines, ophthalmologic preparations and agents used against obstructive airway diseases.

No conflict of interest