Who are the nonresponders to standard treatment with tricyclic antidepressant agents for cyclic vomiting syndrome in adults?

Background: Cyclic vomiting syndrome in adults is a disorder characterized by recurrent and stereotypic episodes of severe nausea and vomiting separated by symptom-free periods.

Aims: To investigate the demographic and clinical characteristics of adult cyclic vomiting syndrome patients not responding to standard tricyclic antidepressant (TCA) therapy.

Methods: A total of 132 adults (62 men) with cyclic vomiting syndrome were followed for a mean of 1.6 years. Of these, 17 (eight men) patients were identified as nonresponders based on the criteria of unchanged, increased or minimally changed (<25%) frequency/duration of episodes and/or emergency department visits/hospitalizations. Demographic and clinical characteristics at baseline and annually up to 4 years were investigated.

Results: The nonresponders were receiving TCAs at an average dose of 90 mg/day compared to a mean dose of 85 mg/day in responders. Compared with the responders, the nonresponders were significantly more likely to have a history of migraine (P < 0.05); co-existing psychological disorders (P < 0.05); chronic marijuana use (P < 0.05) and reliance on narcotics for pain control between cyclic vomiting syndrome episodes (P < 0.05).

Conclusions: (1) Nonresponse to standard therapy in adult cyclic vomiting syndrome patients occurs in approximately 13% and is not explained by under dosing with TCA therapy. (2) The main risk factors for nonresponse are: co-existing migraine headache, psychiatric disorder, chronic narcotic and marijuana use, which should be addressed aggressively when symptom exacerbations continue during attempts to induce remission in cyclic vomiting syndrome with high-dose TCA therapy.