Buprenorphine and the mixed agonists/antagonists nalbuphine and pentazocine, formerly classified as µ-opioid (MOP) receptor antagonists, have more recently been shown to be partial to full agonists of the human MOP receptor. These receptors do not necessarily have to be maximally activated for a full physiological response. Partial agonists can also sufficiently stimulate signaling processes leading to a full analgesic response, as shown by the effectiveness of buprenorphine, nalbuphine and pentazocine in animal pain models and in clinical settings where these drugs induce analgesia with full efficacy without a ceiling effect. Submaximal doses of MOP receptor analgesics combined with submaximal doses of buprenorphine, pentazocine, or nalbuphine result in additive to over-additive antinociceptive effects in animal experiments. Only when doses are given that exceed the therapeutic dose range may the antinociceptive effect be reduced to the effect of either opioid alone. The analgesic effects of pentazocine and nalbuphine combined with morphine are reported to be additive or over-additive in various clinical pain conditions. Buprenorphine, which clinically behaves as a full MOP receptor agonist for pain relief, can be combined with full opioid agonists without precipitating withdrawal. Thus, the overall evidence on the analgesic effects of buprenorphine, pentazocine or nalbuphine combined with opioid analgesics under various clinical pain conditions contradicts the consensus that these compounds diminish MOP receptor analgesia when co-administered with a full MOP receptor agonist.

Colors play a major role in the endoscopic diagnosis of many gastrointestinal conditions. Gastrointestinal endoscopists in the Netherlands are predominantly male (> 90%), and from population data it is to be expected that approximately 8% will have a color vision deficiency. The present study was designed to assess the prevalence of color vision deficiencies amongst Dutch gastrointestinal endoscopists and to determine whether color vision deficiency affects an endoscopist's diagnostic skill. One hundred and thirty-nine gastroenterologists and physicians of internal medicine took an F2 color vision test and assessed nine videofragments of endoscopies. Color vision deficiencies were detected in 8% of Dutch gastrointestinal endoscopists. In one out of the nine video excerpts of endoscopies, a statistically significant difference was detected between test subjects with and without a color vision deficiency. However, this video excerpt showed a green pea, which could not be mistaken for a polyp at polypectomy. The study therefore does not show any effect of color vision deficiencies on endoscopic skills, nor does it show any deviant prevalence of color vision deficiencies amongst Dutch gastrointestinal endoscopists.

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Reduction of N-cyclopropylmet hylenephenylamine by 3,5 -diet hoxycarbon yl-2,6dimet hyl-1,4-d i hydropyrid i ne (Hantzsch ester) results in the exclusive formation of N-cyclopropylmethylaniline, whereas reduction with triphenyltin hydride gives both N-cyclopropylmethylaniline and n-butylaniline, a product of cyclopropane ring cleavage. Research (Z.W.O.).

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