Ko, J. C. H., L. K. Maxwell, et al. (2008). "Pharmacokinetics of lidocaine following the application of 5% lidocaine patches to cats." Journal of Veterinary Pharmacology and Therapeutics 31(4): 359-367.
The use of lidocaine patches to provide local analgesia in cats is increasing. The patch (Lidoderm, Endo Pharmaceuticals) contains 700 mg lidocaine and is 10 cm x 14 cm. It can be cut to a desired size and may be applied to the skin on each side of a surgical incision for post-operative pain relief. Other potential uses include relief of pain from trauma and bruising. This study was conducted to evaluate the systemic and local absorption of lidocaine from topical patches in cats. In a random cross-over design, 8 two-year old cats received either intravenous lidocaine at 2 mg/kg or one lidocaine patch placed on the lateral thorax for 72 hours. Plasma was collected at specified time points and analyzed for lidocaine and its major metabolite. After patch removal, the skin at the site was biopsied and also assayed for lidocaine. The patch produced steady-state lidocaine plasma concentrations. The bioavailability of transdermal lidocaine was 6.3 +/- 2.7% and only 56% of the total drug reached the systemic circulation. Skin lidocaine concentrations were much higher than plasma concentrations. Plasma lidocaine concentrations remained well below systemically toxic concentrations, and no obvious clinical side effects were observed in any of the cats. The researchers conclude that the low systemic absorption rate coupled with high local lidocaine concentrations in the skin support the safe use of lidocaine patches in cats.
>> PubMed AbstractRelated articles:
Weil, A. B., J. Ko, et al. (2007). "The use of lidocaine patches." Comp Contin Edu Pract Vet 29(4): 208-216.
>> PubMed Abstract