Evaluation of sources cited by an exotic animal formulary for supporting drug dosages and reference intervals in...

Formularies are intended to simplify clinical decision-making by collecting evidence-based information on drugs and their dosages. This study assessed the characteristics of sources used to support drug dosages and reference intervals for mammals in a specific exotic animal formulary, and how the sources had changed over five editions.

Each reference supporting drug dosages and reference intervals in the sections for ferrets, rabbits, rodents, hedgehogs and miniature pigs in all five editions of the formulary was evaluated and classified by two independent investigators in terms of the type of source cited. Univariable and multi-variable logistic regression models were built to evaluate changes between editions and sections.

In total, 1338 references supporting drug dosages and 180 references supporting reference intervals were included from all editions of the formulary. Primary sources were cited by 525 (39.2%) and 39 (21.7%) of the drug and reference interval references, respectively. For drug dosages, the current edition of the formulary (2018) cited a higher proportion of primary rather than secondary sources compared with the first edition (odds ratios 3.4, 95% confidence interval 2.1 to 5.6), while for reference intervals there were no significant changes between editions. In the current edition of the formulary, the 168 secondary sources cited for drug dosages included 78 (46.4%) textbooks, 63 (37.5%) reviews, 14 (8.3%) personal communications and 7 (4.2%) other formularies.

A large proportion of references supporting drug dosages and reference intervals in the evaluated sections cited secondary sources. Although modest improvements have been observed over time, practitioners should be aware that the evidence supporting several drugs and dosages was limited, and assess the information within the formulary critically.