3
Pharmacology (Fach) / ANS (Lektion)
- a-1 adrenoreceptors (Distribution/Mechanism/Effects/Antagonists/Agonists) 1. Distribution - blood vessels, smooth muscle 2. Mechanism - activate Phospholipase C 3. Effects - Constriction of vascular smooth muscle --> increase in systolic and diastolic arterial pressure 4. Antagonists a) Hypertension - Doxazosin, Prazosin --> vasodilation, fall in arterial pressure --> side effects include errectile dysfunction and postural hypotension b) Benign prostate hyperplasia - Doxazosin --> relax smooth muscle improving urinary flow c) Local anaesthetics - Lidocaine with adrenaline --> less diffusion, improved specificity 5. Agonists a) Nasal decongestants - pseudoephedrine + oxymetazoline --> decreased nasal secretions by constricting blood vessels in the nose
- a2-adrenoceptors (Distribution/Mechanism/Agonists) 1. Distribution - pre-synaptic cells 2. Mechanism - inhibit the release of NA via inhibition of adenylatecyclase --> decrease of cAMP levels in cell 3. Agonists a) Hypertension - clonidine (selective) - inhibit NA release (resistant hypertension) - Methylnoradrenaline (resistant hypertension)
- b-adrenoceptors (Distribution/mechanism/agonists/antagonists) 1. Distribution a) b1 - heart b) b2 - airway smooth muscle 2. Mechanism - both activate adenylate cyclase and increase cAMP levels within the cell 3. Agonists b1 - chronotrophic and ionotrophic effects --> restore automaticity --> side effects reduction of cardiac efficacy and disturbtion of cardiac rhythm a) Dobutamine - acute stimulation of failing heart 4. Agonists b2 - relaxation of airway smooth muscle a) Salbutamol - symptom relief asthma and COPD --> don't fight underlying inflammation - premature labour --> relaxes uterine smooth muscle and delays delivery (time for mother to receive steroid therapy to mature the baby's lungs 4. Antagonists - b-blockers: effect depends on the level of sympathetic activity (little effect on resting heart rate, cardiac output, arterial pressure under normal circumstances; but exercise tolerance will be reduced) a) Hypertension - reduce cardiac output, sympathetic activity and modify renin release b) Angina pectoris (only b2 antagonists) - improve oxygenation of heart muscle and regulate dysrhythmia c) Side effects - Bradycardia, Hypoglycaemia, Fatigue, Cold extremities, bronchoconstriction