<unk>  is the most widely used opioid in labour and delivery but has fallen out of favour in some countries such as the United States in favour of other opioids, due to its potential drug interactions (especially with serotonergics) and its neurotoxic metabolite, norpethidine. It is still commonly used in the United Kingdom and New Zealand, and was the preferred opioid in the United Kingdom for use during labour, but has been superseded somewhat by diamorphine and other strong semi-synthetic opioids (e.g. hydromorphone) to avoid serotonin interactions since the mid-2000s.<unk>  is the preferred painkiller for diverticulitis, because it decreases intestinal intraluminal pressure. Before 2003 it was on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.
Pethidine
Esketamine
Ketamine
Fentanyl
Aceclidine
Nalorphine
Remifentanil
Procaine