Due to their strong analgesic effect, opioids are used for the alleviation of moderately severe to the most severe acute pain. However, one considerable disadvantage of the use of opioids is the severe side effects associated therewith. Thus they frequently have effects on the gastrointestinal tract, such as obstipation (?), and moreover give rise to respiratory depression, and, on repeated use, to dependency which can lead to misuse. Furthermore, the development of tolerance is a disadvantageous effect.
It has been known for many years that the analgesic effect of opioids is enhanced by the simultaneous administration of organic calcium channel antagonists (Fortschr. Anaesth. 1987, 5). Calcium channel antagonists can be classified into those of the dihydropyridine, benzothiazepine and phenylalkylamine types. They are usually employed for the treatment of cardiovascular disease conditions such as high blood pressure, arrhythmia or angina pectoris. The mode of action of these substances act is based on the selective suppression of the Ca.sup.2+ flux in the Ca.sup.2+ channels of the heart and of the peripheral vascular system. Calcium channels with a high affinity for calcium channel antagonists have also been detected in the brain, so that a central effect of calcium channel antagonists appears probable.
Due to the enhancement of the anti-nociceptive effect of opioids by means of calcium channel antagonists, lower doses of the opioid can be administered for the same analgesic effect. The aforementioned side effects can thereby be reduced. On continued administration, however, the occurrence of dependency, respiratory depression and obstipation (?) must be reckoned with despite these smaller amounts of opioids. Due to the high analgesic efficacy of opioids, however, their use for the treatment of pain cannot to this day be dispensed with.