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EQUINE VETERINARY EDUCATION


Equine vet. Educ. (2019) 31 (5) 278-280 doi: 10.1111/eve.12903


Critically Appraised Topic


Does pergolide therapy prevent laminitis in horses diagnosed with pituitary pars intermedia dysfunction?


E. J. Knowles Bell Equine Veterinary Clinic, Kent and The Royal Veterinary College, London, UK Corresponding author email: e.j.knowles@gmail.com


Background


Pituitary pars intermedia dysfunction (PPID) is a common condition of older horses. It encompasses a spectrum of disease and is associated with various clinical signs. Pergolide (Prascend) is the only licensed medicine for treatment of the clinical signs associated with PPID. Some of these associated clinical signs may be more amenable to therapy than others. Laminitis is a multifactorial condition with elusive pathogenesis. PPID is a risk factor for laminitis, however, its strength as an independent risk factor and interactions with other risk factors remain poorly defined.


Question


In horses diagnosed with PPID, does pergolide treatment reduce the risk of an episode of laminitis (occurrence or recurrence) compared with no treatment or other PPID treatments?


Search strategy


Literature searches were conducted for articles published in English on the Medline database (inception to February 2017) and (by RCVS Knowledge) of the CAB Abstracts database (1973 to February 2017). Search terms included ‘equine’, ‘pituitary’, ‘laminitis’ and ‘pergolide’. Articles were appraised if they were original studies


including at least five cases of PPID treated with pergolide and reported clinical signs of laminitis during/following treatment. Review articles and expert opinion were excluded. The quality of the evidence was appraised based on guidelines from human medicine (Higgins and Green 2011; OCEBM-Levels-of- Evidence-Working-Group 2011). The manufacturers of Prascend (Boeringher Ingelheim) were contacted to request any additional data. Prascend licensing data were obtained from the Veterinary Medicines Directorate and the Food and Drug Administration.


Search outcome


Forty-one papers were initially retrieved, a report of the licensing study was also included. Critical appraisal revealed no suitable evidence to address the question. The most common reasons for not including papers was incomplete reporting of laminitis or a lack of original data (i.e. expert-opinion papers). The question was widened to include studies that


reported improvement in laminitis present at the onset of treatment. No high-quality evidence was found to answer this wider question. The retrieved literature includes clinically useful data and forms a basis for further research but, when


assessed in the context of current appraisal guidelines, the evidence was considered to be limited, at high risk of bias from several sources and incompletely reported. The most informative studies are summarised in Table 1.


Discussion


There is insufficient evidence to conclude that in horses with PPID pergolide treatment reduces the risk of laminitis occurrence or recurrence compared with no treatment or other treatments. The lack of high-quality evidence does not exclude the possibility of a beneficial effect but research should seek to determine if such a benefit exists and the number of animals that would require treatment to prevent a case of laminitis. Improvement of an episode of laminitis that was already


present at the start of treatment was also considered. Several studies report improvement in the clinical signs of laminitis during treatment with pergolide. However, such improvements cannot be attributed to pergolide rather than other interventions such as farriery, rest or analgesia. Similar rates of laminitis improvement have also been reported with cyproheptadine (Perkins et al. 2002) and trilostane (McGowan and Neiger 2003) but comparisons may be hampered by differences between the treated groups. In some cases laminitis developed for the first time during


pergolide treatment, in other cases laminitis recurred or did not improve during pergolide treatment. When considering treatment options clinicians should


weigh the potential benefits of treatment against the risk of adverse effects. Pergolide appears well-tolerated and owner satisfaction with long-term use is reported to be good (Schott et al. 2001; Anon, 2011; Rohrbach et al. 2012). Some studies that described clinical improvement with treatment were not included in the appraisal as signs of laminitis following treatment were not reported clearly. The effects of pergolide treatment on clinical signs of PPID other than laminitis are also relevant to prescribing decisions. Further research could consider the strength of PPID as an


independent risk factor for laminitis and the interactions between insulin regulation and PPID. The risk (incidence/year) of laminitis in horses with PPID is not well-described and reported effects of pergolide treatment on insulin dysregulation are inconsistent. The prevalence of laminitis in the wider population of horses with PPID may be lower than in those that present to veterinary hospitals (McGowan et al. 2013). Any potential benefits of pergolide on laminitis would depend on the circumstances of each patient and their pretreatment risk of laminitis but current evidence does not support the widespread use of pergolide to prevent laminitis.


© 2018 EVJ Ltd


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