What is the recommended dose of ketamine (intramuscular) for relaxation in a patient weighing 100 pounds?

From the Guidelines

For a patient weighing 100 pounds, the recommended dose of ketamine intramuscularly for relaxation is approximately 50 mg, based on a dose of 1 mg/kg. The dose of ketamine can range from 1-2 mg/kg, but a common starting dose is 1 mg/kg, which would be approximately 45 mg for a 100-pound patient, or roughly 50 mg to account for individual variability 1.

Key Considerations

• The onset of action is rapid, usually within 3-4 minutes, with peak effects at 10-15 minutes and a duration of about 30-60 minutes.
• This medication should be administered in a monitored setting with appropriate equipment for airway management, as ketamine can cause respiratory depression, especially when combined with other sedatives.
• The patient should be monitored for vital signs, including blood pressure, heart rate, respiratory rate, and oxygen saturation.

Mechanism and Side Effects

• Ketamine works by blocking NMDA receptors in the brain, producing a dissociative state with analgesia, sedation, and amnesia.
• Side effects may include emergence reactions (hallucinations, vivid dreams), increased blood pressure and heart rate, increased salivation, and nystagmus.
• Having an antisialagogue like glycopyrrolate available may be helpful to manage excessive secretions, as seen in studies such as Pruitt et al 1.

Administration and Monitoring

• The dose should be titrated based on the patient's response and the procedure being performed.
• The patient should be closely monitored during the procedure and recovery period for any adverse effects.
• Studies such as Wathen et al have shown that ketamine can be safe and effective when used appropriately, with minimal adverse effects 1.

From the FDA Drug Label

The initial dose of ketamine hydrochloride injection administered intramuscularly may range from 6.5 to 13 mg/kg. A dose of 9 to 13 mg/kg usually produces surgical anesthesia within 3 to 4 minutes following injection, with the anesthetic effect usually lasting 12 to 25 minutes.

For a patient who weighs 100 pounds (approximately 45.4 kg), the recommended dose of ketamine IM for relaxation would be:

• 6.5 to 13 mg/kg x 45.4 kg = 295 to 587 mg for the lower and upper bounds of the dose range, respectively, but
• 9 to 13 mg/kg x 45.4 kg = 408 to 589 mg for the typical dose range. Given the context that the question is asking for the dose to relax the patient and not necessarily induce surgical anesthesia, a dose at the lower end of this range may be more appropriate, but the exact dose should be individualized and titrated to the desired clinical effect 2.

From the Research

Ketamine Dosage for Relaxation

To determine the recommended dose of ketamine for relaxation in a patient weighing 100 pounds, we must consider the available evidence.

• The dosage of ketamine can vary based on the specific use case, such as sedation or treatment of depression.
• According to the study 3, the dose of ketamine used in the Brain Injury and Ketamine study is 1 mg/kg/h by continuous infusion.
• For a patient weighing 100 pounds (approximately 45.36 kg), the calculated dose would be approximately 45.36 mg/h.
• However, this study does not provide information on the use of ketamine for relaxation via intramuscular (IM) administration.
• Another study 4 discusses the pharmacology of ketamine but does not provide specific dosage recommendations for relaxation.
• Studies 5, 6, and 7 also do not provide specific guidance on the dosage of ketamine for relaxation via IM administration.

Considerations for Administration

• It is essential to note that ketamine dosing can vary significantly depending on the route of administration, the specific condition being treated, and individual patient factors.
• The studies provided do not offer direct evidence for the use of ketamine IM for relaxation in a patient weighing 100 pounds.
• In clinical practice, the dosage of ketamine for sedation or relaxation is typically determined based on the patient's weight, the desired level of sedation, and the specific clinical context, often requiring consultation of clinical guidelines or expert opinion.

Available Information

• Given the information available, there is no direct evidence to support a specific dosage of ketamine IM for relaxation in a patient weighing 100 pounds.
• Further research or consultation with a medical professional is necessary to determine the appropriate dosage for this specific use case.