Purpose: Treatment of opioid-resistant pain and of opioid-induced neurotoxicity.
What is Ketamine: It is a “dissociative anesthetic” (the mind is ‘dissociated’ from the body and pain), meaning a patient ‘appears to remain awake’ but is actually unconscious and feels no pain when given full anesthetic doses. With sub-anesthetic doses, pain/agitation are reduced without ‘loss of awareness/consciousness’. It is particularly beneficial for neuropathic pain and opioid-resistant or difficult pain syndromes; and can reduce the amount of narcotic required.
Physiological Effects to be expected (uncommon w/ sub-anesthetic doses): tachycardia, increased secretions, diplopia, myoclonus, increased BP [occasionally hypotension].
Adverse Effects: increased salivation; hallucinations and vivid dreams when emerging from full anesthetic doses (but usually preventable if use a benzodiazepine prior to or while giving ketamine). Avoid in patients with psychosis history.
Dosing Guidelines: Can be given po, subQ, IM, IV, intranasal. The IV form is readily absorbed when given po/subling. Mix with fruit juice/compote to mask taste. If given subling, give no other med or food/drink for 2 minutes following the ketamine.
Generally, oral dose given Qhs, depending on response, and is usually needed only for a few days [similar to steroid bursts – e.g. 100mg Qday po x 3days] but can be given for longer period.
Protocol for Conscious Patient:
1. Obtain VS [BP, HR, RR, temp].
2. Encourage patient/family to read this Ketamine Information handout and explain it.
3. Administer 25mg po or sublingual test dose.
4. After 1 hr, if patient indicates pain reduced, instruct patient/family to take 50mg hs that night.
5. Ativan 1mg should be taken qhs as well, plus q a.m. prn [if too “dreamy” feeling].
6. Visit patient daily and review pain level; if pain not controlled [to patient’s goal, e.g. 3/10], increase dose by 50mg each night to maximum 300mg for five more days.
7. Alternative schedule may be prescribed: 25-100mg po qid x 1wk.
8. Consider reducing opioid by 25-50% at initiation of ketamine.
9. Patient continues to use scheduled and breakthrough pain meds, keeping log of doses.
1. Fine PG. Ketamine: from anesthesia to palliative care. AAHPM Bulletin 2003.
2. Fitzgibbon EJ, Viola R. Parenteral ketamine as an analgesic adjuvant for severe pain: development and retrospective audit of a protocol for a palliative care unit. J Palliative Med 2005. 8;1:49-57.
3. Prommer E. Ketamine: routes and techniques of administration. AAHPM Annual Meeting, Austin, TX 2009.