Physico-chemical, pharmacological and toxicological properties of fomocaine metabolites

Fomocaine (4-[3-(4-phenoxymethylphenyl)-propyl] -morpholine, CAS 17692-39-6) is a highly effective Local anaesthetic of low toxicity. The drug, which causes no allergic response, was introduced in the German Extrapharmacopoeia (DAC). Fourteen metabolites are formed after oral administration to rat and beagle dog. Less than 5 % fomocaine are excreted unchanged. The metabolites were synthesized and their physico-chemical properties were investigated. No metabolite caused a surface or conduction anaesthesia with the exception of 2-hydroxyfomocaine (O/Se 4). After topical and parenteral administration irritation could not be observed. All metabolites except O/Se 10 and O/Se 11 showed a lower toxicity than fomocaine. In both species O/Se 10 and O/Se 11 are formed only in a small amount and are detoxified by conjugation.