Objective: To report a case in which complete relief of pain associated with gastroparesis, with promotion of gastric emptying, was achieved with administration of phentolamine.
Case summary: A 37-year-old opiate-tolerant female with a history of recurrent abdominal pain, gastroparesis, cyclic vomiting syndrome, and migraine headaches was admitted to the emergency department (ED) with severe acute abdominal pain, nausea, and vomiting. The patient had been previously implanted with a permanent gastric electrical stimulator and she was adherent to her prokinetic, antiemetic, analgesic, and migraine prophylactic medications. Pain relief was achieved rapidly and completely in the ED with sympatholysis by administration of intravenous phentolamine 0.5 mg/kg over 60 minutes, with continuous cardiac monitoring. At a 2 month follow-up visit, the patient reported chronic pain relief, and a decrease in opiate doses was maintained by oral administration of clonidine 0.1 mg twice daily.
Discussion: Gastroparesis represents a difficult treatment challenge because management of gastric dysmotility and the accompanying severe abdominal pain is often mutually exacerbating and ineffective. Sympatholysis by intravenous phentolamine provided profound and immediate relief of acute gastroparesis-related abdominal pain in our patient. The mechanism of phentolamine is believed to be receptor blockade at alpha-adrenergic receptors and, therefore, inhibition of the peripheral sensitizing effects of circulating norepinephrine. Although action at a peripheral nerve level is presumed, modulation of alpha-adrenoreceptors receptors is also possible at the dorsal root ganglion or at other central nervous system sites.
Conclusions: The dramatic relief of acute pain in gastroparesis by phentolamine observed in this case would warrant investigation of a larger, controlled case series. Patients who respond to intravenous sympatholysis may likewise be candidates for longer term sympathetic modulation with oral sympatholytics.