Focus on Alternative and Complementary Therapies
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Focus Alternat Complement Ther©2005 Pharmaceutical Press
Focus Altern Complement Ther 2003; 8: 522–3
To determine the prevalence of clinical investigations of NHP–drug pharmacokinetic interactions and assess the methodological quality of these trials.
Data sources: we searched electronic databases from their inception until December 2002; we reviewed reference lists from published reports and contacted experts in the field for missed or unpublished studies. Study selection: eligible studies were clinical investigations of the interaction between a NHP and the metabolism of a regulated medication in humans. We excluded articles that only investigated metabolism of a NHP or examined food-drug or NHP–NHP interactions.
Data synthesis: 28 clinical investigations studying an average of 13 participants/study (95% CI 11–15), examined drug interactions with six different herbal preparations. All trials were pharmacokinetic studies. Most studies (20) used a before–after design; six studies used controls (three of them used placebos), eight studies randomised the sequence of administration or the participants to study arms or periods and two studies blinded participants or investigators. Six reports justified their sample size. Healthy volunteers took drug for study purposes in 24 studies; four studies examined patients taking the indicated drug. Investigators assayed the NHP in only 14 of 35 evaluations. Most studies (25) examined interactions at the steady state; three examined single-dose pharmacokinetics and two examined both.
Our review indicates that this literature is very limited, with only 28 reports of just six NHPs being identified, despite extensive literature searching. We also found that the studies we identified (1) contain few safeguards against the intrusion of bias, such as random and concealed allocation of participants, inclusion of controls, and blinding, (2) used poor pharmacokinetic methods, such as limited assaying of the NHPs to document their composition, and (3) show wide variation in methodologies without evidence of widely-accepted standards of research practice.
