Also some cardiac effects D Increased renal blood flow. This group of drugs is useful for resuscitation of seriously ill patients, and for the treatment of hypotension in theatre. All of these drugs act directly or indirectly on the SNS, but the effect of each varies according to which sympathetic receptor the drug has greatest affinity for. The duration of action also varies. Direct acting drugs act by stimulating the SNS receptor whereas indirect acting drugs cause the release of noradrenaline from the receptor which produces the effect.
Some drugs have a mixed effect.
Adrenaline acts on a 1, b 1 and b 2 receptors. Increased heart rate and force of contraction produce an increase in cardiac output. At higher doses the vasoconstrictor effects of a 1 stimulation become more apparent, causing the cool pale extremities of a frightened person. Adrenaline mobilises glucose from glycogen and raises blood sugar. Side effects Ventricular arrhythmias, hypertension.