Mode of action: Apomorphine is a centrally acting drug for the treatment of ED; it is not approved in the United States, although it is available in Europe. CNS control of sexual function is thought to be maintained through a balance of inhibitory and excitatory systems, influenced by androgens and by erectogenic stimuli from centers of the brain concerned with sight, sound, smell, touch, and cognition. A variety of neurotransmitters are involved but, simplistically, the primary neurotransmitter of central sexual inhibition is serotonin, and of central sexual excitation, dopamine. Apomorphine activates dopamine D2 receptors in the hypothalamus and has the potential to both initiate an erection and enhance responsiveness to erectogenic stimuli.
Use in practice: Proper counseling about the use of any therapy is vital to a successful outcome, but particularly so with ED therapy. Apomorphine is taken sublingually and it is essential that the patient be told to pop it under the tongue, and to allow it to dissolve slowly rather than suck or swallow it. If it is swallowed, it will probably be ineffective, because of the very high proportion of drug metabolized on the first pass through the liver. The 2’mg tablet is pentagonal, and the 3’mg, triangular. Read the rest of this entry »