Phytomedicine. 2000 Mar; 7(1): 73-81.

The psychodynamic and pharmacodynamic effects of drugs: a differentiated evaluation of the efficacy of phytotherapy.

Schulz V.

The therapeutic usefulness of medicines is nowadays usually measured in terms of parameters devised in the artificial surroundings of a double blind clinical trial. The difference between the active drug and the placebo is accepted as being the same as the desired overall effect. Yet, when applied to whole categories of medicines, this yardstick can be misleading, as has become apparent from the discussion which has recently arisen regarding the genuine and the illusory pharmacodynamic effects of synthetic antidepressants. Differentiated analysis of a representative number of placebo-controlled studies has shown that when used for depressive conditions, the psychodynamic components contribute far more to the overall effect than do the pharmacodynamic components. In this respect, modern synthetic antidepressants are no better than Hypericum products of plant origin. Among other things, this means that for depressive states and similar indications, the safety, tolerability and acceptability of a medicine must be given much greater weight than its pharmacodynamic effects as assessed simply by testing against a placebo. The quantification of the two therapeutic components, as can be accomplished by a placebo-controlled drug trial, has revealed that the overall outcome of therapy for various important indications of this kind is attributable predominantly to the psychodynamic component. It may reasonably be assumed that the contribution made by the pharmacodynamic effects to the overall therapeutic response will amount to only about 20-50%. This raises questions regarding the clinical relevance and economic value of placebo-controlled studies. When assessing data on drug efficacy for the purpose of licensing applications, greater attention should be given to this reality.