Multimodal perineural analgesia with combined bupivacaine-clonidine-buprenorphine-dexamethasone: safe in vivo and chemically compatible in solution.

OBJECTIVES: The use of adjuvants in regional anesthesia has increased. However, there are knowledge gaps pertaining to 1) in vivo local tissue effects of these adjuvants; and 2) chemical compatibility and solubility of these drugs in solution with each other and with local anesthetics. This study addresses these gaps in knowledge. DESIGN: In vivo rat safety/toxicopathology study and analytical chemistry study. SETTING: Collaborating Good Laboratory Practice laboratories under the direction of the university-based principal investigator. METHODS: Single-injection formulations of clonidine, buprenorphine, and dexamethasone were combined with either bupivacaine or midazolam, and were administered to groups of rats. Post-injection behavior was monitored to assess changes related to the block. A continuous infusion of bupivacaine, clonidine, and dexamethasone was administered to another group of rats, and behavioral effects were recorded. After 15 days, rats were sacrificed and their nerves/dorsal root ganglia were examined by the pathologist. Samples of combined drug solutions were processed at an analytical chemistry laboratory for compatibility, solubility, and stability. RESULTS: Each of the single-injection formulations produced reversible sensory and/or motor block. None of the study drugs caused damage to any of the nerve segments or related tissue. The text describes the concentrations at which compatibility and solubility of the combined drug solutions were achieved. CONCLUSIONS: Four-drug single-injection formulations are described that 1) had compatible and stable concentrations in solution; and 2) produced reversible nerve block without causing long-term motor or sensory deficits or damage to sciatic nerves/dorsal root ganglia.

Extrapyramidal symptoms following administration of oral perphenazine 4 or 8 mg: an 11-year retrospective analysis.

BACKGROUND: Perphenazine is a treatment option in postoperative nausea and vomiting (PONV) prophylaxis. Chronic administration and high dose are known to cause extrapyramidal system (EPS) dysfunction at a frequency of 8%, but the incidence of acute EPS after a single 4 or 8 mg dose is unknown. OBJECTIVE: A retrospective analysis of patient medication billing data and departmental quality records was performed (January 2001 to 10 July 2012) to identify patients who experienced EPS dysfunction after oral perphenazine. DESIGN: A retrospective analysis. SETTING: Surgical outpatients presenting to any one of 10 hospitals in the area of Pittsburgh, Pennsylvania, USA. PATIENTS: Overall, 45 766 patients received 4 or 8 mg of perphenazine before same-day surgery. MAIN OUTCOME MEASURES: EPS dysfunction was defined as acute dystonia, akathisia or pseudoparkinsonism. Records were reviewed to determine the likely number of reactions to perphenazine, the nature of these reactions and impact on patient care. RESULTS: There were four 'likely' cases of EPS dysfunction, and two 'possible' cases. Five reported events were consistent with akathisia, with the sixth being a dystonic reaction. All six patients had resolution of symptoms, with five receiving intravenous diphenhydramine for treatment. The incidence of EPS dysfunction was 1.3 events per 10 000 patients (95% confidence interval (CI) 0.4 to 3.0, based on six events). All patients who experienced reactions pre-operatively were able to proceed to surgery without complications or delay. One patient required unplanned admission and 3-h observation owing to sedation from diphenhydramine. The incidence of EPS dysfunction after oral perphenazine is low. Reactions that did occur were mild and easily treated. CONCLUSION: Given the infrequent side effects, this single, low dose of perphenazine should be encouraged as a low-risk adjunct to any multimodal PONV prophylaxis regimen, based on the selection criteria described.