ABSTRACT
Botulinum neurotoxins induce a prolonged muscle paralysis by specifically blocking the release of neuronal transmitters from peripheral nerve junctions. Potency testing of toxin and antitoxin therapies is entirely dependent on mouse lethality bioassay which is associated with extreme suffering of large numbers of animals to ensure high precision. The mouse phrenic nerve-diaphragm assay is an ex vivo assay that closely mimics in vivo respiratory paralysis offering substantial refinement and reduction in the number of animals used. A range of botulinum antitoxin standards, one licenced product and experimental antitoxins were tested for neutralising potency using ex vivo hemidiaphragm assay and compared with in vivo determined activities. Overall, there was an excellent agreement between neutralising activity detected by the two assay systems and for each toxin serotype using only 4-7 replicates for each product (almost perfect concordance for type A antitoxins: ρ = 0.997, and substantial concordance for type B antitoxins: ρ = 0.991 and type E antitoxins: ρ = 0.964, respectively). These findings confirm that the mouse nerve-diaphragm preparation can provide a functional ex vivo replacement assay for specific, sensitive and precise assessment of toxin and antitoxin activity.
Subject(s)
Botulinum Antitoxin/analysis , Diaphragm/drug effects , Phenytoin/pharmacology , Phrenic Nerve/drug effects , Toxicology/methods , Animals , Botulinum Antitoxin/classification , Botulinum Antitoxin/immunology , Immunoassay/methods , Immunologic Factors/analysis , Immunologic Factors/classification , Immunologic Factors/immunology , Male , Mice , Mice, Inbred BALB C , Sensitivity and SpecificityABSTRACT
Botulinum neurotoxins induce a prolonged muscle paralysis by specifically blocking the release of neuronal transmitters from peripheral nerve junctions. The current method for assessing the potency of botulinum toxin and antitoxins is the mouse LD50 assay. The mouse phrenic nerve-diaphragm assay is an in vitro assay that closely mimics in vivo respiratory paralysis. In this study, we have further improved the assay by using gelatin as a non-frothing alternative to albumin and investigated the effects of botulinum toxin serotypes A, B and E on phrenic nerve-hemidiaphragms from out-bred MF1 and in-bred Balb/c mice. Improved reproducibility was found with in-bred mice. Balb/c mice were also found to be much less sensitive to type B toxin perhaps indicating differences in the expression of receptor components. Hemidiaphragm preparations from Balb/c mice were approximately 7 times more sensitive to type A toxin and 7-12 times more sensitive to type E toxin relative to type B toxin. These findings indicate that when fully optimised the mouse nerve-diaphragm preparation can provide a functional in vitro model for accurate and reproducible assessment of toxin activity.
Subject(s)
Botulinum Toxins, Type A/toxicity , Botulinum Toxins/toxicity , Diaphragm/drug effects , Phrenic Nerve/drug effects , Toxicity Tests/methods , Albumins , Animals , Animals, Outbred Strains , Gelatin , In Vitro Techniques , Male , Mice , Mice, Inbred BALB CABSTRACT
There is considerable interest in developing new non-steroidal anti-inflammatory drugs (NSAIDs) formulations with faster onset of analgesic action like fast dissolving tablets. An open-label, randomized, single dose, crossover study with a 18 days washout period was conducted in 16 healthy volunteers to compare the pharmacokinetic profile of 20 mg piroxicam freeze-dried tablet (Proxalyoc, Cephalon) with that of 20 mg piroxicam capsule (Feldene, Pfizer). T(lag) with freeze-dried tablet was three times shorter than with capsule (21.6 min versus 59.4 min). Mean AUC(0-30 min), mean AUC(0-1 h), mean plasma concentrations at 15 min, 30 min and 1 h post-dose were significantly higher with the freeze-dried tablet than with the capsule, indicating that piroxicam was more rapidly absorbed from the freeze-dried tablet with higher plasma concentrations achieved at shorter intervals after dosing. The 90% confidence intervals of the ratios of means C(max), AUC(0-t), AUC(0-infinity) and T(1/2) all fell within the acceptance range of 0.8-1.25, demonstrating the bioequivalence of the two formulations. Although the bioavailability of the two formulations was similar, the administration of piroxicam as a freeze-dried tablet gave a much faster absorption rate during the first hour after dosing than the capsule formulation. This faster absorption is an obvious advantage for the treatment of acute episodes of pain.
