Anesthetic that is been used for humans and animals as the drugs called special k. may deliver almost instant relief in some of the most troublesome cases of bipolar depression. It has been known for several years that small doses of the drug (ketamine) can relief major depression. In bipolar disorder sometimes called manic-depressive illness, patents cycle between periods of elation and severe depression, and the depressive phase carries a high risks of suicide. It is commonly treated with mood stabilizers including lithium, anticonvulsants and some anti psychotics often in complex combinations.

Both mania and depression usually improves on taking the drug ketamine, but when the depression remains, it is notoriously difficult to treat, so a fast-acting medicine with lasting effects would have obvious advantages. ketamine probably act by limiting the action of one type of brain receptor that moves nerve signals between neurons. Because ketamine is already approved as an anesthetic, physicians could use it off label for other purposes. 

 Researches show that 10 patents in the study had taken lithium or the anticonvulsant valproate for at least 4 weeks without getting better. They were randomly assigned to receive an intravenous infusion of either ketamine or a placebo saline solution two weeks apart, with each receiving the drug on one occassion and the saline solution on the other. the tests shows that the ketamine patents had significantly fewer depressive symptoms than those who receive the placebo. 

Ketamine is the only anaesthetic available which has analgesic (pain relieving), hypnotic (sleep producing) and amnesic (short term memory loss) effects. When used correctly it is a very useful and versatile drug.

Ketamine is available in three different concentrations 10mg/ml, 50mg/ml and 100mg/ml. 50mg/ml is most commonly stocked since it can be used for i.m. administration or diluted for i.v. use.

Routes of Administration

Ketamine may be given intravenously (induction 1-2mg/kg, maintenance 0.5mg/kg) or intramuscularly (induction 5-10mg/kg, maintenance 3-5mg/kg) for anaesthesia or orally (15mg/kg for a child to a maximum of 500mg for an adult) for sedation.

Central Nervous System

Ketamine produces dissociative anaesthesia (detached from surroundings). This means that unlike with other anaesthetic agents the patient may have their eyes open and make reflex movements during the operation. It has a slower onset after an i.v. bolus (1-5 minutes). The duration of action depends on the route of administration (20-30 minutes for i.m. and 10-15 minutes for iv).

Ketamine provides very good analgesia and may be used without any other analgesics intraoperatively. Consideration does then have to be given however to postoperative pain relief. Co-administration of opiates or tramadol intraoperatively can reduce the amount of ketamine required for maintenance of anaesthesia and therefore reduce the incidence and duration of postoperative hallucinations. This does however increase the risk of apnoea during the operation.

There were no serious side effects, although about 10 percent of both those receiving ketamine and those taking the placebo got an headache or nausea, or feeling wooozy after the infusions. The adverse effects associated only with ketamine include feeling strange, and having a dry mouth. After about 80 minutes there were no differences in side effects between the ketamine and placebo groups