Clinical trial NCT01385904: Blood Levels of Ketamine in Patients Using Topical Application of 10% Ketamine Gel for Neuropathic Pain
Official title: Plasma Concentrations of Ketamine and Norketamine in Patients Using Topical Application of 10% Ketamine for Neuropathic Pain.
Study type: OBSERVATIONAL
Overall status: UNKNOWN
Conditions: Neuropathic Pain.
Lead sponsor: London Health Sciences Centre Research Institute OR Lawson Research Institute of St. Joseph's
Sponsor class: OTHER
First posted: 2011-06-30
Enrollment: 15
Sex: ALL
Minimum age (years): 18
Maximum age (years): 80
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: CASE_ONLY
Time perspective: PROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: Patients attending the St Josephs Hospital pain clinic with chronic neuropathic pain.

Brief summary: The purpose of this research study is to measure how much, if any, ketamine is absorbed into the blood stream after ketamine gel is applied to the skin. The investigators expect that the topical administration will provide pain relief locally, at the site of pain, but not be absorbed into the bloodstream and thus not cause side effects. This research will help assess the safety of this drug by measuring the blood concentrations of the drug.

Ketamine is a general anesthetic drug but also has excellent pain relieving qualities. It has been used to relieve chronic pain by administering intravenously, by mouth, or as an injection beneath the skin. When given these ways ketamine can occasionally cause side effects like dizziness, nausea, nightmares, agitation, hallucinations. Recently it has been used topically for patients with neuropathic pain in order to avoid the dizziness and nausea side effects.

Neuropathic Pain can be partially caused by the misfiring of small nerve fibers close to the area of pain. By applying it on the skin, it is expected the drug can penetrate the skin and act directly on the small nerve fibers. The advantage is that less drug will get into the blood circulation. Up to now, it has not been carefully studied how much of the drug appears in the circulation after application on the skin.


Eligibility criteria: Inclusion Criteria:

* Patients with peripheral, focal neuropathic pain such as or complex regional pain syndrome following surgery, bony, soft tissue trauma or nerve trauma, associated with significant allodynia and hyperalgesia who score equal to or greater than 4 in the DN4 questionnaire.
* Duration of pain more than 3 months.
* Ability to speak English adequately to consent to and participate in the study

Exclusion Criteria:

* Allergy to ketamine
* Severe medical illnesses like, e.g. unstable angina, tachyarryhthmias, renal or hepatic failure
* History of psychosis.
* Patients who are already on oral ketamine treatment.
* Patients who are taking HIV Antiretrovirals: (indinavir, nelfinavir, ritonavir saquinavir); Antibiotics: (clairithromycin, itraconazole, ketoconazole, telithromycin,fluconazole, erythromycin); Calcium Channel Blockers (verapamil, diltiazem),Amiodarone, Ciprofloxacin. (These drugs inhibit CYP 3A4 enzyme which metabolises ketamine)

Primary outcomes:
Secondary outcomes:
Other outcomes:
Locations:
city: London
country: Canada
facility: Pain Clinic, St. Joseph's Health Care London Hospitals
state: Ontario
Study officials:
affiliation: Western University, Canada
name: Patricia Morley- Forster, MD, FRCPC
role: PRINCIPAL_INVESTIGATOR
References:
citation: Poyhia R, Vainio A. Topically administered ketamine reduces capsaicin-evoked mechanical hyperalgesia. Clin J Pain. 2006 Jan;22(1):32-6. doi: 10.1097/01.ajp.0000149800.39240.95.
citation: Finch PM, Knudsen L, Drummond PD. Reduction of allodynia in patients with complex regional pain syndrome: A double-blind placebo-controlled trial of topical ketamine. Pain. 2009 Nov;146(1-2):18-25. doi: 10.1016/j.pain.2009.05.017. Epub 2009 Aug 22.
citation: Zapantis G, Csoka I, Csanyi E, Horvath G, Eros I. Evaluation of ketamine systemic absorption from topical preparations. Short Communication. Acta Biol Hung. 2006 Sep;57(3):387-9. doi: 10.1556/ABiol.57.2006.3.12.
citation: Clements JA, Nimmo WS, Grant IS. Bioavailability, pharmacokinetics, and analgesic activity of ketamine in humans. J Pharm Sci. 1982 May;71(5):539-42. doi: 10.1002/jps.2600710516.
citation: Pedersen JL, Galle TS, Kehlet H. Peripheral analgesic effects of ketamine in acute inflammatory pain. Anesthesiology. 1998 Jul;89(1):58-66. doi: 10.1097/00000542-199807000-00011.
citation: Lynch ME, Clark AJ, Sawynok J, Sullivan MJ. Topical 2% amitriptyline and 1% ketamine in neuropathic pain syndromes: a randomized, double-blind, placebo-controlled trial. Anesthesiology. 2005 Jul;103(1):140-6. doi: 10.1097/00000542-200507000-00021.
citation: Grant IS, Nimmo WS, Clements JA. Pharmacokinetics and analgesic effects of i.m. and oral ketamine. Br J Anaesth. 1981 Aug;53(8):805-10. doi: 10.1093/bja/53.8.805.