Possible Interaction: Caffeine and Phenylephrine

“Prenatal exposure to caffeine increased pressor responses and vasoconstrictions to phenylephrine , accompanied by enhanced membrane depolarization.”

“10 mM caffeine (CAF) increased of [Ca2+]i in NPE and PE (NPE > PE) and sometimes produced very slow oscillations with an interval of 10 to 25 s. Prior administration of CAF strongly suppressed the effects of ACH, CARB, EPI, PHE , histamine, and adenosine 5-triphosphate (ATP).”

“Kinetic analysis of these data indicated that caffeine reduced the Ca2+ content of the same intracellular compartment depleted by phenylephrine , whereas forskolin depleted a different intracellular Ca2+ store.”

“Since caffeine is known to inhibit phosphodiesterase, the additional stimulation of both syntheses by caffeine plus phenylephrine may be due to the synergistic effect of increases in cAMP and [Ca2+].”

“On the other hand, Takagi, Takayanagi and Tomiyama (4, 5) have reported that the relaxing effects of papaverine and isoprenaline, a beta-adrenergic stimulant, … that caffeine and imidazole, which influence phosphodiesterase activity, considerably modify the responses of the taenia to isoprenaline and papaverine, while the action of phenylephrine, … caffeine ….”