1. S. Kaivola, Outpatient Clinic, Bulevardi 22, 00120 Helsinki 12, Finland; J. Parantainen and T. Österman, Research Laboratories of Medica Pharmaceutical Co., Ltd., P.O. Box 325, 00101 Helsinki 10, Finland; H. Timonen, Lauttasaari Medical Center, Gyldenintie 2, 00200 Helsinki 20, Finland