hiccups are a common side effect of opiates , also yawing is fairly common. hiccuping is a sudden, involuntary contraction of the diaphragm which occurs at the same time as a contraction of the voice box (larynx) and total closure of the glottis, effectively blocking air intake. the glottis is the middle part of the larynx, where the vocal cords are located. experts are not sure what causes hiccups and why we do them. most agree that they are often triggered by minor stomach upsets. sometimes, hiccups are said to have a psychological, rather than a physical cause - however, nobody really knows.
opiates are known the upset the stomach, and in my opinion, the aact of hiccuping is trying to get whatever is bothering your stomach out of your stomach. opiates and ulcers are related and ulcers also cause hiccps.