Abstract: The present invention relates to compounds and pharmaceutical compositions useful for treating pain. The invention also relates to methods of treating or alleviating pain in mammals, comprising administering to a mammal suffering from pain, a pain-alleviating amount of a compound of the general formula (I) or (II).

Abstract: The invention relates to the use of branched chain fatty acids (BFAs) and their derivatives for inhibition of the activity of P-glycoprotein (P-gp). In particular, the invention relates to the use of BFAs and their derivatives in the treatment of multi-drug resistant (MDR) tumors associated with increased activity of P-glycoprotein. The invention also relates to the use of the above-mentioned molecules for administration of biologically active molecules and diagnostic agents into cells associated with increased activity of P-gp, and for increasing accumulation of biologically active molecules and diagnostic agents in organs protected by biological barriers.