A pharmacodynamic–pharmacokinetic (PD–PK) study on the effects of Danshen (Salvia miltiorrhiza) on midazolam, a model CYP3A probe substrate, in the rat

This study investigated the effect of Danshen on the pharmacodynamic–pharmacokinetic (PD–PK) effects of midazolam, a model CYP3A probe substrate. The effects of acute and 3-day Danshen treatment on the pharmacokinetics of a low dose midazolam (10 mg/kg, i.p.) were determined in vivo in the rat. Danshen (200 mg/kg, i.p.) treatment decreased midazolam clearance by 16%, with increases in the AUC by 22% and the half-life by 14%. 3-Day Danshen treatment (200 mg/kg/day, i.p.) for 3 days decreased the clearance, with increases in the T1/2 and AUC. The effects of acute and 3-day Danshen on midazolam-induced hypnosis, serum 1′-hydroxy-midazolam to midazolam ratio and hepatic CYP3A protein expression were determined in the rat. Danshen treatments (100–200 mg/kg, i.p. and 200–500 mg/kg, p.o.) increased the sleeping time (p < 0.001) produced by a hypnotic dose of midazolam (50 mg/kg, i.p.) without affecting the sleep latency. Serum 1′-hydroxy-midazolam to midazolam ratio after the hypnotic dose of midazolam was decreased after intraperitoneal Danshen treatment (200 mg/kg) but not after oral treatment at up to 500 mg/kg. All the treatment groups with Danshen, after intraperitoneal and oral administration, decreased hepatic CYP3A protein expression (p < 0.05) by about 25%. The results confirmed that Danshen had no enzyme inducing effects on rat CYP3A.