This issue has come up once, and only once, in Question 15 from the first paper of 2001.
A hiccup, or singultus, or synchronous diaphragmatic flutter, is a myoclonic spasm of the diaphragm, which is stimulated by the phrehnic nerve. The signal to hiccup is sent from the nucleus tractus solitarius.
This signal can be stimulated by a number of pathological conditions. A brief review lays these bare:
The review article remarks that "The more than 100 forms of physical or pharmacological treatment for intractable hiccups include prayers to St Jude, the patron saint of lost causes". As reliable remedies, the author recommends to raise the PaCO2 and to vigorously stimulate the posterior pharynx. Apparently, chlorpromazine remains the most consistently effective agent.