Cassia angustifolia is a species of a plant from the Senna family that
has traditionally been used as a laxative in different herbal products
and commercial medicines. There are few described interactions between
Senna and drugs, most of them related to electrolyte disturbances due to
concomitant use with other laxatives or due to increased intestinal
transit that may limit the absorption of drugs with low bioavailability.
We present a case with supratherapeutic trough concentration of
tacrolimus in a liver transplant patient after concomitant intake of
tacrolimus and a herbal product based on Cassia angustifolia, suggesting
a possible drug-plant interaction by means of P-glycoprotein. We observe
an increase in their plasma concentration 2.8-fold and the AUC 2.1-fold.