Challenging the challenge: A randomized controlled trial evaluating the inflammatory response and pain perception of healthy volunteers after single-dose LPS administration, as a potential model for inflammatory pain in early-phase drug development.

BACKGROUND AND AIMS: Following an infection, cytokines not only regulate the acute immune response, but also contribute to symptoms such as inflammatory hyperalgesia. We aimed to characterize the acute inflammatory response induced by a human endotoxemia model, and its effect on pain perception using evoked pain tests in two different dose levels. We also attempted to determine whether combining a human endotoxemia challenge with measurement of pain thresholds in healthy subjects could serve as a model to study drug effects on inflammatory pain. METHODS AND RESULTS: This was a placebo-controlled, randomized, cross-over study in 24 healthy males. Twelve subjects were administered a bolus of 1 ng/kg LPS intravenously, and twelve 2 ng/kg LPS. Before days of placebo/LPS administration, subjects completed a full study day without study drug administration, but with identical pain threshold testing. Blood sampling and evoked pain tests (electrical burst and -stair, heat, pressure, and cold pressor test) were performed pre-dose and at frequent intervals up to 10hr post-dose. Data were analysed with a repeated-measures ANCOVA. For both dose levels, LPS induced an evident acute inflammatory response, but did not significantly affect any of the pain modalities. In a post-hoc analysis, lowering of pain thresholds was observed in the first 3 h after dosing, corresponding with the peak of the acute inflammatory response around 1-3 h post-dose. CONCLUSION: Mild acute systemic inflammation, as induced by 1 ng/kg and 2 ng/kg LPS intravenous administration, did not significantly change pain thresholds in this study. The endotoxemia model in combination with evoked pain tests is not suitable to study acute inflammatory hyperalgesia in healthy males.

Detection and elimination of adventitious agents in continuous cell lines.

The National Veterinary Services Laboratories (NVSL) routinely monitors continuous cell lines (CCL's) used for veterinary biologicals and diagnostic virology. All veterinary biologicals produced in CCL's must follow the master seed concept which limits the use of the master seed CCL to up to 20 passages beyond the passage level characterized and deposited at NVSL. All CLL's are evaluated for the presence of adventitious agents such as mycoplasma, bovine viral diarrhea virus, and other bacteria and viruses. Previously, CCLs were evaluated for tumorigenicity by the Syrian hamster cheek pouch method; however, this procedure has now been eliminated. The adventitious agents most frequently detected in CCL's have been bovine viral diarrhea virus and mycoplasma. Our laboratory has consistently found that the source of bovine viral diarrhea contamination of CCLs has been the use of contaminated fetal bovine cell culture enrichment serum. Gamma irradiation at 2.5-3.5 megarads at -40 degrees C of carefully screened fetal bovine serum has been used in the Diagnostic Virology Laboratory for over 10 years. If the irradiated serum is used at a final concentration of 10 percent, there is no untoward effect on cell susceptibility for virus propagation or cell culture growth. Gamma irradiation has also been demonstrated to be a very efficient inactivator of mycoplasma. Specific conditions utilized by our laboratory to preserve fetal bovine serum cell culture growth factors while eliminating adventitious bovine viral diarrhea virus will be presented.

Acute methemoglobinemia induced by topical benzocaine and lidocaine.

Acute methemoglobinemia may result from the use of several local anesthetic agents. Benzocaine (Cetacaine) spray has been shown previously to cause methemoglobinemia in two patients when applied topically to the mucous membranes. We describe a patient with respiratory failure following trauma who had two episodes of acute methemoglobinemia, one after the topical application of benzocaine and the second following lidocaine administration for endotracheal intubation. The episodes occurred more than 20 hours apart, and no other drugs known to induce methemoglobinemia were given. On both occasions, intravenous methylene blue was effective in correcting the disorder.