Clinicians and patients should beware of possible decreases in the systemic bioavailability of conventional drugs when taken concomitantly with St John 's wort
OBJECTIVE To determine the method ological quality of clinical trials that examined possible interactions of St John 's wort with conventional drugs , and to examine the results of these trials .
Effects of St. John's wort (Hypericum perforatum) on tacrolimus pharmacokinetics in healthy volunteers.
Tacrolimus is an immunosuppressant approved for the prevention of rejection following transplantation and is a substrate for CYP3A and P-glycoprotein . A pharmacokinetic interaction between St. John 's wort ( antidepressant herbal product and inducer of CYP3A and P-glycoprotein ) and tacrolimus was evaluated in 10 healthy volunteers . The pharmacokinetics of tacrolimus were obtained from serial blood sample s collected following single oral doses ( 0.1 mg/kg ) prior to and during an 18-day concomitant St. John 's wort dosing phase ( 300 mg orally three times daily ) . Coadministration of St. John 's wort significantly decreased  tacrolimus AUC ( 306.9 microg.h/L + /- 175.8 microg.h/L vs. 198.7 microg.h/L + /- 139.6 microg.h/L ; p=0.004 ) and increased apparent oral clearance ( 349.0 mL/h/kg + /- 126.0 mL/h/kg vs. 586.4 mL/h/kg + /- 274.9 mL/h/kg ; p=0.01 ) and apparent oral volume of distribution at steady state ( 11.5 L/kg + /- 4.3 L/kg vs. 17.6 L/kg + /- 9.6 L/kg ; p=0.04 ) . St. John 's wort appears to induce  tacrolimus metabolism , most likely through induction of CYP3A and P-glycoprotein
Clinicians and patients should beware of possible decreases in the systemic bioavailability of conventional drugs when taken concomitantly with St John 's wort
OBJECTIVE To determine the method ological quality of clinical trials that examined possible interactions of St John 's wort with conventional drugs , and to examine the results of these trials .