The Effect of Drotaverine on Gastrointestinal Motility and Heart Rate Variability in Normal, Resting Horses

Abstract

The impact of a non-anticholinergic spasmolytic drug (drotaverine hydrochloride) on 23 heart rate (HR), HR variability (HRV) and gastrointestinal tract (GIT) motility in the normal, resting 24 horses was determined. Ten adult riding horses had ECG recordings for 180 minutes after treat-25 ment with drotaverine (180 mg) or saline. Horses from the drotaverine group presented a de-26 creased of GIT contraction for two hours after treatment, but also showed drowsiness. Drotaverine 27 caused a reduction in cardiac vagal modulation of HR at T30 (P=0.050) and T60 (P=0.008) compared 28 to those receiving saline. RMSSD and high frequency (HF) recorded significantly low values after 29 drotaverine treatment by the end of the study, suggesting a decrease in parasympathetic activity. 30 HRV analysis indicated that drotaverine decreased both the low frequency (LF) and Lf/HF ratio 31 reflecting a decrease in sympathetic system. Non linear parameters registered low values after 32 drotaverine administration pointing a diminished in parasympathetic (for SD1) and sympathetic 33 (for SD2) activity. Decreased HRV was suggestive for a pervasive state of sympathetic hypervigi-34 lance of horses. The marked effect of drotaverine on HRV and GIT function in horses should be 35 taken into consideration when evaluating a clinical response to this drug in diseases associated 36 with smooth muscle spasm.