Ketamine as an adjuvant to opioids for cancer pain.

This is an update of a review first published in 2003 and updated in 2012.Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of refractory cancer pain, when opioids alone or in combination with appropriate adjuvant analgesics prove to be ineffective. Ketamine is known to have psychomimetic (including hallucinogenic), urological, and hepatic adverse effects.