High-dose midazolam and the attenuation of the contractile response to vasoconstrictors in coronary artery segments.
OBJECTIVE
Benzodiazepines may cause hypotension and are reported to interfere with smooth vascular muscle activity. The aim was to elucidate the influence of three different benzodiazepines on the vascular reactivity of coronary arteries.


METHODS
Using the model of isolated vessels, we studied the impact of midazolam (0.15, 1.5, 15 microg mL(-1)), diazepam (0.1, 1.0, 10 microg mL(-1)) and flunitrazepam (0.01, 0.1, 1.0 microg mL(-1)) on the contractile responses to histamine (2 x 10(-5) mol L(-1)) and serotonin (3 x 10(-5) mol L(-1)) in isolated intact and denuded coronary arteries.


RESULTS
Midazolam significantly attenuated the contractile response when administered in high concentrations (15 microg mL(-1)). This effect was more pronounced in intact than in denuded preparations (histamine: -22.7 versus -7.3%, P = 0.0079; serotonin: -47.1 versus -15.9%, P < 0.0001). Diazepam and flunitrazepam exerted no significant effects on the vascular tone of coronary arteries.


CONCLUSIONS
Midazolam, but not diazepam or flunitrazepam, attenuates the contractile responses to vasoconstrictors in concentrations beyond those used in clinical practice. This effect is in part mediated by endothelial factors.
Klockgether-Radke
A P
AP
Georg-August University of Göttingen, Department of Anaesthesiological Research, Centre of Anaesthesiology, Emergency and Intensive Care Medicine, Göttingen, Germany. klockgether-radke@gmx.de
Thudium
A
A
Frerichs
A
A
Kettler
D
D
Hellige
G
G
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular; D005445:Flunitrazepam / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D066298:In Vitro Techniques; D008874:Midazolam / Q000008:administration & dosage / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D014151:Anti-Anxiety Agents; D006993:Hypnotics and Sedatives; D014662:Vasoconstrictor Agents; D012701:Serotonin; D005445:Flunitrazepam; D006632:Histamine; D003975:Diazepam; D008874:Midazolam