Transitioning Cats from Lente Insulin to Protamine Zinc Insulin
Andrew Bugbee, DVM, DACVIM, University of Georgia
In the Literature
Gostelow R, Hazuchova K, Scudder C, Forcada Y, Church D, Niessen SJM. Prospective evaluation of a protocol for transitioning porcine lente insulin-treated diabetic cats to human recombinant protamine zinc insulin. J Feline Med Surg. 2018;20(2):114-121.
The Research …
This study* assessed a protocol for transitioning cats from a porcine-source lente insulin (LI) to a human-recombinant protamine zinc insulin (PZI). Although both insulin formulations have been shown to be efficacious in the management of feline diabetes mellitus, PZI has been reported to exhibit a longer duration of action in a model of healthy cats.1-3
Inclusion criteria included diagnosis of diabetes mellitus within the previous 5 months, twice-daily LI injections for at least 6 weeks, and eating a low-carbohydrate, high-protein diet for at least 10 days. Cats (n = 22) were screened for concurrent conditions and underwent a 24-hour glucose curve to assess response to LI (median dose, 0.5 U/kg). A validated clinical scoring system (Diabetic Clinical Score) and patient and owner quality-of-life (QOL) assessments were serially evaluated at set time points over the study period. Following determination of glycemic responses to LI, patients were transitioned to twice-daily PZI at manufacturer-recommended starting doses (median dose, 0.5 U/kg). Glucose curves were serially assessed over a 12-week period, with PZI doses adjusted using a preinsulin and nadir glucose concentration-based protocol.
After the 12-week PZI period, diabetic cats had statistically significant reductions in serum fructosamine, lower clinical scores, and lower administered insulin doses; QOL scores were indicative of improved QOL. Although true duration of action is difficult to define when insulin is administered twice daily, 6 LI-treated cats were documented to have short durations of action (<9 hours); only 2 PZI cats were found to have an action duration <9 hours. All cats noted to have durations of insulin action <9 hours were found to experience improved durations when treated with the opposite formulation.
Periods of subclinical and clinical hypoglycemia were uncommon (15.8%) but were noted with both insulin formulations. Although the study was not designed to prove superiority of one insulin formulation, 22.7% of cats entered remission within 12 weeks of being transitioned to PZI, which suggests that PZI is a viable treatment option for diabetic cats.
… The Takeaways
Key pearls to put into practice:
PZI may result in improved diabetic outcomes in cats as compared with LI, which is likely attributable to a consistently more appropriate duration of insulin action.
In cases of poor duration of insulin action, cats may exhibit more favorable responses when transitioned to a different insulin type.
Transition to PZI can be safely accomplished using manufacturer-recommended starting doses, with subsequent dose titrations directed by serial glycemic monitoring of the patient’s insulin response.
*This study was supported by Boehringer Ingelheim.