Influence Of Vicoprofen?? On Endogenous Opioid Peptides Following Exercise-induced Muscle Damage

Abstract

PURPOSE To determine the effects of Vicoprofen®, ibuprofen, and placebo on the responses of endogenous opioid peptides following resistance exercise-induced muscle damage. METHODS Thirty-six healthy men (age: 22.8 yrs; height: 178.8 ± 6.2 cm; body mass 78.9 ± 13.7 kg; body fat: 15.8 ± 6.5%) volunteered to participate in the study after giving written informed consent. Following baseline testing, participants performed an established eccentric exercise protocol (i.e., 10 sets of 8–10 repetitions of eccentric knee extensions in a seated stack plate knee extension weight training machine with a weight equivalent to 120% of the previously determined concentric 1RM). A randomized, double-blind, placebo-controlled, repeated dose design was employed in this investigation. Each participant was evaluated for pain 24 hours post and randomly assigned to an experimental group: Vicoprofen® (VIC), Ibuprofen (IBU), or placebo (P). Medication was prescribed four times daily beginning with the day following completion of the eccentric exercise protocol (i.e., Vicoprofen® (hydrocodone bitartrate 7.5 mg with ibuprofen 200 mg), and Ibuprofen 200 mg. Blood was sampled via venipuncture from the antecubital vein at rest and at 24,48,72,96, and 120 hrs following the eccentric exercise damage protocol. Muscle damage was determined via magnetic resonance imaging techniques and plasma CK analysis. Plasma samples were immediately frozen at −80o C and thawed once for assay. Plasma proopiomelanocortinß- endorphin (B-End) and plasma proenkephalin-peptide F (P-F) concentrations were analyzed via radioimmunoassay after HPLC extraction and sample preparation. RESULTS For plasma B-END no significant changes were observed in the resting values over the recovery period among any of the treatment conditions. Conversely for plasma proenkephalin P-F, VIC and IBU had significantly (P <0.05) higher plasma concentrations of P-F above placebo at 24, 48, 72, and 96 hrs with VIC higher IBU and placebo conditions at 120 hrs. Significant resting elevations were observed for P-F from pre-exercise at 48,72,96 and 120 hrs for VIC; at 72 and 96 hrs for IBU; and at 72 for placebo treatment. Less tissue damage, improved physical function as well as reduced pain was observed for the VIC condition over IBU and placebo. CONCLUSIONS These data indicate that a combined opiate/anti-inflammatory medication appears to offer greater pain relief than an anti-inflammatory drug alone and such exogenous medications appear to be differentially influencing the peripheral (adrenal medulla) versus the central (hypo-pituitary) opioid neuroendocrine responses as measured by plasma concentrations.