From the Guidelines
Intravenous (IV) ketamine has a rapid onset of action, typically beginning within 1 minute after administration, and a short duration of action, lasting approximately 10-15 minutes for its anesthetic effects, as reported in the most recent and highest quality study 1. The onset and duration of IV ketamine can be influenced by various factors, including the dose administered and the individual patient's response.
- The typical adult dosing range for procedural sedation is 0.5-1 mg/kg IV given slowly over 1-2 minutes, while subanesthetic doses for pain or depression (0.1-0.5 mg/kg) may be administered as a slow infusion over 40-60 minutes.
- Ketamine's rapid onset is due to its high lipid solubility, allowing quick passage across the blood-brain barrier, while its redistribution from the brain to peripheral tissues accounts for its short duration, as noted in 1 and 1.
- Patients should be monitored for potential side effects, including tachycardia, hypertension, emergence reactions, nausea, and respiratory effects, though ketamine generally preserves respiratory drive better than other sedatives, as reported in 1 and 1.
- Recovery monitoring should continue for at least 1-2 hours after administration to ensure safe discharge, considering the potential for prolonged psychoactive and analgesic effects, as mentioned in 1 and 1.
From the FDA Drug Label
Following intravenous administration, the ketamine concentration has an initial slope (alpha phase) lasting about 45 minutes with a half-life of 10 to 15 minutes. This first phase corresponds clinically to the anesthetic effect of the drug The redistribution half-life of ketamine from the CNS to slower equilibrating peripheral tissues (beta phase) is 2.5 hours.
The onset of IV ketamine is rapid, with an anesthetic effect that lasts around 10 to 15 minutes. The duration of action is longer, with a redistribution half-life of 2.5 hours 2.
From the Research
IV Ketamine Onset and Duration
- The onset of IV ketamine is rapid, with maximum plasma concentrations achieved quickly, especially with nasal administration 3.
- The duration of IV ketamine's effects can vary depending on the dose and individual response, but it is generally used for short-term pain management 4, 5.
- Studies have shown that IV ketamine can be effective for immediate pain relief at 15 minutes, but its overall effect in comparison to opioids for improving pain has not shown a statistically significant difference 6.
- The use of IV ketamine as an adjunct to opioids can result in lower total opioid doses and fewer repeat doses of analgesia, with a tolerable side effect profile 7.
- The specific duration of IV ketamine's effects is not consistently reported in the studies, but it is often used in clinical settings for acute pain management, with effects lasting from several minutes to several hours 3, 4, 5, 7.