Effects of lidocaine, codeine and vadocaine hydrochloride on platelet aggregation in human platelet-rich plasma.

Lidocaine and vadocaine hydrochloride (2',4'-dimethyl-6'-methoxy-3-(2-methylpiperidyl)propionanilide+ ++ hydrochloride, OR K-242-HCl; INN: vadocaine), which is structurally related to lidocaine, inhibited the second phases of human platelet aggregation induced by adenosine diphosphate (ADP, 10 mumol/l) or epinephrine (10 mumol/l) and partly aggregation induced by collagen (2.5 micrograms) at concentration relevant to local anesthetic action (0.1-1.0 mmol/l). Codeine was effective at slightly higher concentrations. The concomitant formation of thromboxane B2 (TXB2) was inhibited at similar concentrations. The aggregation induced by arachidonic acid (200 mumol/l) and the first phases of ADP (10 mumol/l)- or epinephrine (10 mumol/l)-induced aggregations were inhibited by all the compounds at the concentrations 1-10 mmol/l, codeine being the most potent inhibitor. The only exception was vadocaine, which inhibited the first phase of epinephrine-induced aggregation at concentrations greater than or equal to 0.25 mmol/l. Vadocaine may possess a2-adrenergic blocking activity. At low concentrations (less than or equal to 0.1 mmol/l), all the compounds stimulated/tended to stimulate the second phase of ADP-induced aggregation and concomitant formation of TXB2. They strongly stimulated TXB2 formation induced by exogenous arachidonic acid even at concentrations causing inhibition of aggregation. Codeine was the most and vadocaine the least potent in this respect. Lidocaine as well as vadocaine (0.1 mmol/l) and codeine (1.0 mmol/l) potentiated the antiaggregatory effect of dibutyryl-cyclic AMP (dB-cAMP) on the ADP-induced aggregation. Lidocaine (0.1 mmol/l) and codeine (1.0 mmol/l) similarly potentiated the effect of the adenylate cyclase stimulator prostaglandin E1 (PGE1).