Pethidine is a strong medicine for very bad pain. Doctors give it in hospital, and for many years it was especially used for women in labour — the hours of giving birth. It is an opioid, in the same broad family as morphine: it changes how the brain feels pain, and it can make you sleepy or strange. In the United States the same drug is usually called meperidine; an old American brand name is Demerol. You cannot buy it in a normal shop; it is locked up and controlled. Though actually, many hospitals use it less than they once did. It does not last long in the body, and a leftover chemical it turns into can be unkind to the nerves if doses pile up. For a learner, the useful fact is this: it is a legal hospital pain drug, not a fever pill, and not a street name you should guess at.

配西汀（醫院用的強效止痛藥；大陸稱哌替啶。華語裡常聽到的舊商品名是杜冷丁）