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(789)
S48 (788) Topical morphine bioavailability in volunteers J Paice, J Von Roenn, J Hudgins, L Luong, T Krejcie, M Avram; Northwestern University; Robert H. Lurie Comprehensive Cancer Center, Chicago, IL Although most patients with cancer-related pain obtain relief with available therapies, swallowing difficulties or intestinal obstruction preclude oral analgesic delivery. Topical morphine may provide an alternate delivery form but morphine bioavailability from a topical gel formulation has not been reported in humans. Therefore, we conducted a randomized, placebo controlled, double-blind, crossover study of five healthy volunteers after they provided institutionally approved written informed consent. They were admitted to the General Clinical Research Center (GCRC) of Northwestern University twice, being randomly assigned to receive either one mL of morphine compounded at 10 mg/mL in pluronic lecithin organogel (PLO) base (ExcelleRx, Philadelphia, PA) applied to the wrist and one mL of normal saline administered subcutaneously or one mL of topical drug-free PLO base and one mL of subcutaneous morphine 3 mg/mL on the first occasion and the opposite combination on the second occasion. Seventeen blood samples were collected from 5 min to 10 h after dose administration for determination of plasma morphine concentrations. Plasma samples were prepared by solid-phase extraction and morphine concentrations measure by an LCMS-MS technique with a linear range of 0.5 – 500 ng/ml. Bioavailability of the topical formulation was estimated from doses and areas under the curves, assuming the subcutaneous dose bioavailability was 100%. The median bioavailability of morphine compounded in a PLO base and administered topically to volunteers was less than 2%. Despite a report that topical morphine is effective in controlling chronic arthritis pain, the present results are consistent with the report that morphine was minimally absorbed transdermally from a PLO formulation in dogs. These results suggest that transdermal administration of morphine compounded in a PLO base is unlikely to provide relief of cancer-related pain. Supported in part by a grant from ExcelleRx.
(789) An open-label pharmacokinetic study in humans of a 4% amitriptyline 2% ketamine topical cream D Everton, D Bhagwat, M Damask; EpiCept Corporation, Englewood Cliffs, NJ Topically delivered pain medications can provide adequate pain relief without the side-effects of systemically delivered drugs. This open-label, pharmacokinetic study in 36 healthy adults was designed to determine plasma levels of a topically delivered cream containing 4% amitriptyline and 2% ketamine (NP-1). The level of quantitation was (0.5 ng/mL). 4 mL of NP-1 cream were applied b.i.d. during a 48 hour period. Safety/tolerability were assessed and blood samples were collected up to 96 hours after first application. Plasma amitriptyline levels were above 0.500 ng/mL after the second application, through 60 hours after the last application. The mean Cmax of 1.676 ng/mL occurred 72 hours after the first application. The highest amitriptyline concentration observed at any one time point was 5.91 ng/mL. The terminal elimination phase for amitriptyline had not been reached in most of the subjects. Plasma ketamine levels were above 0.500 ng/mL within several hours after the first application up to the last observation at 96 hours. The highest single ketamine concentration was 10.7 ng/mL. The mean ketamine Cmax of 5.198 ng/mL occurred at 41.4 hours. Terminal elimination was ongoing during the final 48 h of the study in the majority of the subjects. The PK parameter values for both drugs were age-group independent. NP-1 was found to be safe and well tolerated across all groups. Mild, transient application site irritation was the most common adverse event and occurred in 11% of subjects. Prior studies utilizing a twice-daily local application of NP-1 in the treatment of various neuropathies suggest that significant pain relief can be achieved. This study confirms that the efficacy is due to topical action as only sub-therapeutic blood levels of both drugs are observed.
Abstracts (790) Effect of lidocaine patch on thermal thresholds and experimental pain M Wallace, V Lam, G Schulteis; University of California San Diego, La Jolla, CA Currently, there is a growing interest in the use of topical agents for the treatment of pain; therefore, there is a need to validate the use of human experimental pain using topical analgesics. This study evaluated the effects of topical lidocaine on intradermal capsaicin induced pain and hyperalgesia. Thirteen subjects entered into a double-blind, placebo-controlled, randomized study. A baseline quantitative neurosensory test (QST) was performed on the volar aspect of each forearm. A placebo patch and a lidocaine patch was applied to the volar aspect of each forearm. The arms were randomized to placebo and lidocaine patch. After four hours of application the right forearm patch was removed, QST was repeated, and capsaicin (10l, 10 mg/ml) was injected intradermally at the site of application. Pain scores were measured at the time of injection and every 2.5 minutes for 10 minutes. Ten minutes after the capsaicin injection, the hyperalgesic area and flare response were mapped and QST was repeated. At the completion of the testing on the right forearm, the left forearm patch was removed and the procedures described for the right forearm were repeated for the left forearm. Prior to the capsaicin injection the lidocaine patch resulted in a significant increase in the cool and warm thresholds and a significant decrease in hot pain thresholds from baseline. There was no effect on cold pain thresholds. Although there was a trend for increase in touch and touch pain thresholds, it did not reach statistical significance. The lidocaine patch had no effect on the pain, flare or hyperalgesia, This study demonstrated differential effects of the lidocaine patch on skin sensation. Since there was a lowering of the hot pain thresholds, it is not surprising that lidocaine patch had no effect on intradermal capsaicin induced pain and hyperalgesia.
D30 - Other (791) Hyperbaric oxygen treatment decreases edema and mechanical hypersensitivity in animal models of acute inflammation and arthritis H. Wilson; University of Texas at Arlington, Arlington, TX Society for Neuroscience abstract
(789) An open-label pharmacokinetic study in humans of a 4% amitriptyline 2% ketamine topical cream D Everton, D Bhagwat, M Damask; EpiCept Corporation, Englewood Cliffs, NJ Topically delivered pain medications can provide adequate pain relief without the side-effects of systemically delivered drugs. This open-label, pharmacokinetic study in 36 healthy adults was designed to determine plasma levels of a topically delivered cream containing 4% amitriptyline and 2% ketamine (NP-1). The level of quantitation was (0.5 ng/mL). 4 mL of NP-1 cream were applied b.i.d. during a 48 hour period. Safety/tolerability were assessed and blood samples were collected up to 96 hours after first application. Plasma amitriptyline levels were above 0.500 ng/mL after the second application, through 60 hours after the last application. The mean Cmax of 1.676 ng/mL occurred 72 hours after the first application. The highest amitriptyline concentration observed at any one time point was 5.91 ng/mL. The terminal elimination phase for amitriptyline had not been reached in most of the subjects. Plasma ketamine levels were above 0.500 ng/mL within several hours after the first application up to the last observation at 96 hours. The highest single ketamine concentration was 10.7 ng/mL. The mean ketamine Cmax of 5.198 ng/mL occurred at 41.4 hours. Terminal elimination was ongoing during the final 48 h of the study in the majority of the subjects. The PK parameter values for both drugs were age-group independent. NP-1 was found to be safe and well tolerated across all groups. Mild, transient application site irritation was the most common adverse event and occurred in 11% of subjects. Prior studies utilizing a twice-daily local application of NP-1 in the treatment of various neuropathies suggest that significant pain relief can be achieved. This study confirms that the efficacy is due to topical action as only sub-therapeutic blood levels of both drugs are observed.
Abstracts (790) Effect of lidocaine patch on thermal thresholds and experimental pain M Wallace, V Lam, G Schulteis; University of California San Diego, La Jolla, CA Currently, there is a growing interest in the use of topical agents for the treatment of pain; therefore, there is a need to validate the use of human experimental pain using topical analgesics. This study evaluated the effects of topical lidocaine on intradermal capsaicin induced pain and hyperalgesia. Thirteen subjects entered into a double-blind, placebo-controlled, randomized study. A baseline quantitative neurosensory test (QST) was performed on the volar aspect of each forearm. A placebo patch and a lidocaine patch was applied to the volar aspect of each forearm. The arms were randomized to placebo and lidocaine patch. After four hours of application the right forearm patch was removed, QST was repeated, and capsaicin (10l, 10 mg/ml) was injected intradermally at the site of application. Pain scores were measured at the time of injection and every 2.5 minutes for 10 minutes. Ten minutes after the capsaicin injection, the hyperalgesic area and flare response were mapped and QST was repeated. At the completion of the testing on the right forearm, the left forearm patch was removed and the procedures described for the right forearm were repeated for the left forearm. Prior to the capsaicin injection the lidocaine patch resulted in a significant increase in the cool and warm thresholds and a significant decrease in hot pain thresholds from baseline. There was no effect on cold pain thresholds. Although there was a trend for increase in touch and touch pain thresholds, it did not reach statistical significance. The lidocaine patch had no effect on the pain, flare or hyperalgesia, This study demonstrated differential effects of the lidocaine patch on skin sensation. Since there was a lowering of the hot pain thresholds, it is not surprising that lidocaine patch had no effect on intradermal capsaicin induced pain and hyperalgesia.
D30 - Other (791) Hyperbaric oxygen treatment decreases edema and mechanical hypersensitivity in animal models of acute inflammation and arthritis H. Wilson; University of Texas at Arlington, Arlington, TX Society for Neuroscience abstract