Comparative study of cardiovascular, neurological and metabolic side effects of 8 narcotics in dogs. Pethidine, piritramide, morphine, phenoperidine, fentanyl, R 39 209, sufentanil, R 34 995. II. Comparative study on the epileptoid activity of the narcotics used in high and massive doses in curarised and mechanically ventilated dogs.

The experimental design, described in part I, was again used here. The electrocortical activity was registered with an EEG amplifier using a bipolar derivation of needle electrodes fixed in the scalp of a dog in the fronto-occipital position. In this situation the convlusion threshold for the 8 substances is as follows: pethidine 20 mg.kg-1 I.V., piritramide 30, morphine 180, phenoperidine 4, R 39 209 5, fentanyl 4, sufentanil 4 and R 34 995 10 mg.kg-1 I.V. Comparing the I.V. doses producing severe convulsions with the doses necessary for deep surgical analgesia a safety margin of neurological toxicity was calculated. This was for pethidine 2.2, for piritramide 6.6, for phenoperidine 16, for R 39 209 62.5, for morphine 72, for fentanyl 160, for sufentanil 1 000 and for R 34 995 10 000. It is concluded that for pure narcotics there exists an inverse relationship between analgesic potency and neurological toxicity which is always accompanied by a hyperactivity of the automatic nervous system. Factors modifying the convulsive level of the narcotics are still under investigation. In the meanwhile it can be stated that the association of a strong narcotic with flunitrazepam, droperidol or etomidate will increase the convulsion threshold of the morphinomimetics.