Clinical Pharmacology and Use of Morphin,Ketamin and Midazolam

摘要

The pharmacological properties of three drugs commonly used in emergency medical systems (EMS) - morphin, ketamine und midazolam -are described. Morphin, a potent analgesic interacts with the opioid receptor. Side effects include respiratory depression, hypotension and bra-dykardia. Morphin is hepatically degraded to active metabolites, which are excreted renally. 7-10 mg are administered intravenously, clinical effects may be antagonized by naloxone. Ketamine produces analgesia, sedation and anesthesia in a dose dependent manner. Effects are mainly due to non-compatitive antagonism at the NMDA-receptor. Side effects include respiratory depression, psychotomimetic derangement, blurred vision and hypersalivation. Ketamine is hepatically metabolized and renally excreted. Onset of action is rapid, due to high lipophilicity. Ketamine is available as racemic mixture of S+ and R~ ketamine, or as pure S+-ketamine. S+-ketamine is given at dosages of 0.125-0.25 mg/kg to achieve analgesia. When the effect is to be achieved with the racemate, dosages must be more than doubled. Midazolam interacts with the benzodiaze-pine subunit of the GABA-receptor. Main effects include sedation, anxiolysis, anterograde amnesia and an increase of the seizure threshold; a relevant side effect is respiratory depression. Onset is rapid following intravenous administration. Midazolam is hepatically metabolized and renally excreted. Attention must be paid to drug interactions. For sedation, 1-2.5 mg/kg are given. Flu-mazenil is available as antagonist. Morphin, ketamine and midazolam are powerful drugs, the use of which shall be restricted to experienced physicians. In order to assess and balance effects and risks of these drugs, thorough understanding of their clinical pharmacology is mandatory.