The pressor and mydriatic effects of tropicamide-phenylephrine combination, plain tropicamide, and plain phenylephrine

Marion Alva Mesina-Bayana, MD, Milagros H. Arroyo, MD

To evaluate the pressor and mydriatic effects of different concentrations of tropicamide and phenylephrine eye drops: tropicamide 0.5% (Mydriacyl), phenylephrine hydrochloride 2.5% (Mydfrin), tropicamide-phenylephrine
combination 0.5%/0.5% (Sanmyd-P), and self-prepared mixture (1:1 dilution) of commercially prepared tropicamide 0.5% and phenylephrine 2.5%.

A prospective, randomized, double-blind study was carried out involving 160 eyes of 80 patients who were randomly assigned into four groups to receive phenylephrine + tropicamide 0.5%/0.5% (Group A), tropicamide + phenylephrine 0.2%/1.25 (Group B), tropicamide 0.5% (Group C), or phenylephrine 2.5% (Group D). The main outcome measures were systolic, diastolic, and mean arterial pressures; pulse rate; and horizontal pupillary diameter determined at 10-, 20-, 30-, 45-, and 60-minute intervals postinstillation. Repeated measures analysis of variance and Tukey’s honestly significant difference were used to analyze outcomes.

There was no significant increase in the systolic and diastolic blood pressure within each group and between groups. The mean increase or decrease in heart rate from baseline did not show a significant difference. Tropicamidephenylephrine 0.5%/0.5% (Group A) and tropicamide-phenylephrine 0.25%/ 1.25% (Group B) yielded the highest mean increase in pupil size across time.

Tropicamide-phenylephrine 0.5%/0.5% and tropicamide-phenylephrine 0.25%/1.25% attained better dilation per unit time than the other treatment groups. No significant effect on blood pressure and heart rate was seen in all groups.

Keywords: Tropicamide, Phenylephrine, Mydriatic, Blood pressure, Heart rate