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Concentration‐Effect Relationships for Intravenous Alfentanil and Ketamine Infusions in Human Volunteers: Effects on Acute Thresholds and Capsaicin‐Evoked Hyperpathia
Author(s) -
Wallace Mark S.,
Ridgeway Beri,
Leung Albert,
Schulteis Gery,
Yaksh Tony L.
Publication year - 2002
Publication title -
the journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 116
eISSN - 1552-4604
pISSN - 0091-2700
DOI - 10.1177/0091270002042001008
Subject(s) - capsaicin , ketamine , alfentanil , anesthesia , hyperalgesia , medicine , analgesic , intradermal injection , placebo , erythema , pharmacology , threshold of pain , nociception , surgery , fentanyl , receptor , alternative medicine , pathology , immunology
The authors have extended preclinical studies on pain to human volunteers by examining the effects of intravenous alfentanil and ketamine on acute sensory thresholds and facilitated processing induced by intradermal capsaicin. Eleven healthy subjects received targeted plasma concentrations of alfentanil, ketamine, and placebo followed by neurosensory testing (thermal and von Frey hair thresholds). After completing the tests at the highest plasma level, intradermal capsaicin was injected into the volar aspect of the left forearm, and the flare response and hyperalgesia to von Frey hair, stroking, and heat were assessed. Alfentanil significantly elevated cool and warm thresholds and decreased capsaicin‐induced stroking hyperalgesia. Ketamine significantly decreased capsaicin‐induced von Frey hair hyperalgesia. Both drugs resulted in a significant elevation of von Frey hair‐induced pain thresholds and a decrease in capsaicin‐induced pain. These studies suggest that experimental human pain models may be used to study analgesic pharmacology and may serve as important methods for defining the analgesic efficacy of drugs in phase I clinical trials.