2015 ACVIM Forum Research Abstract Program

Plasma samples from hypertensive cats treated with amlodipine at two first opinion practices were identified retrospectively. Hypertension was diagnosed based on a systolic blood pressure (SBP) ≥170 mmHg on 2 consecutive visits or SBP ≥160 mmHg with concurrent evidence of hypertensive retinopathy. All cats were started on 0.625 mg amlodipine q24h and invited back for a blood pressure re-check 1-2 weeks later. Adequate control was defined as SBP <160 mmHg and if SBP was ≥160 mmHg the dose was increased to 1.25 mg/cat/day, with another re-check 1-2 weeks later. Blood samples were collected at the first visit SBP control was adequate. Plasma amlodipine concentration was determined using high-performance liquid chromatography with tandem mass spectrometric (LC/ MS/MS) detection. A linear mixed effects model with Bonferroni post hoc comparison was used to compare SBP at hypertensive visit and SBP at first controlled visit between cats on 0.625 mg (A) and 1.25 mg (B). Plasma amlodipine concentration was compared between A and B using a Mann-Whitney U-test. Results are presented as mean AE sd or median [IQR] . Univariable linear regression models were performed with absolute change in SBP with amlodipine treatment as the dependent variable and plasma amlodipine concentration, dose in mg/kg, time since last dosing, treatment time in days, and plasma potassium and creatinine concentration as explanatory variables. Variables were log transformed if needed to meet normality criteria and variables significant at the P < 0.1 level were included in the multivariable model.