Adrenaline pharmacology

It is a catecholamine, which is secreted mainly by adrenal medulla. Adrenaline is a direct acting nonselective adrenergic agonist

1. ADRENERGIC AGONISTS AND PHARMACOLOGY OF ADRENALINE Dr. S P SRINIVAS NAYAK, Assistant Professor, SUCP, HYD. Telangana , India.

2. Classification of Sympathomimetics / Adrenergic Agonists Classification of On the basis of their therapeutic use: 1. Nasal decongestants: Phenylephrine , xylometazoline , pseudoephedrine, oxymetazoline , naphazoline

3. 2. For allergic reactions ( anaphylactic shock): Adrenaline

4. 3. To raise the blood pressure in shock: Dopamine, noradrenaline, ephedrine , phenylephrine , methoxamine , mephentermine

5. 4. As bronchodilator: Salbutamol , terbutaline , salmeterol , formoterol

6. 5. As cardiac stimulant: Adrenaline , isoprenaline , dobutamine .

7. 6. As CNS stimulant: Amphetamine , dextroamphetamine .

8. 7. For local vasoconstrictor effect: Adrenaline. Adrenaline is used as a local haemostatic to control bleeding following tooth extraction and during surgical procedures in nose, throat, larynx , or in cuts, injuries etc. because of its vasoconstrictor effect.

9. As anorexiant : Dextroamphetamine , mazindol , phentermine , sibutramine

10. ADRENALINE (EPINEPHRINE) It is a catecholamine, which is secreted mainly by adrenal medulla. Adrenaline is a direct acting nonselective adrenergic agonist

11. PHARMACOLOGICAL ACTIONS OF ADRENALINE 1. Cardiovascular system(CVS) a . Heart: Adrenaline is a powerful cardiac stimulant Increase in heart rate (positive chronotropic effect). Increase in myocardial contractility (positive inotropic effect). Increase in conduction velocity (positive dromotropic effect b. Blood vessels and BP: Blood vessels of the skin and mucous membranes are constricted by adrenaline. It also constricts renal, mesenteric, pulmonary and splanchnic vessels, but dilates the blood vessels of skeletal muscle and coronary vessels .

12. 2. RESPIRATORY SYSTEM: Adrenaline rapidly relaxes (beta.2 ) bronchial smooth muscle. It is a potent bronchodilator but has a short duration of action. It inhibits the release of inflammatory mediators from mast cells (beta.2 ). It also reduces secretions and relieves mucosal congestion by vasoconstrictor effect (alpha.1 ).

13. 3. Gastro intestinal tract( GIT) It relaxes the smooth muscle of the gut. It reduces the intestinal tone and peristaltic movements. Mostly it causes Constipation

14. 4. Bladder : It relaxes the detrusor muscle and contracts the sphincter. As a result, it may cause difficulty in urination .

15. 5. CNS : In therapeutic doses, adrenaline does not cross the BBB and hence CNS effects are very minimal. But in high doses, it may cause headache, restlessness and tremor.

16. 6. METABOLIC EFFECTS: Adrenaline increases the blood glucose level by: Stimulating hepatic glycogenolysis (beta2 ), which is the predominant effect. Reducing insulin secretion. Decreasing the uptake of glucose by peripheral tissues.

17. 7. Other effects on each cell It reduces plasma K+ levels by promoting the uptake of K+ into the cells, particularly into the skeletal muscle. It causes hypokalemia

18. PHARMACOKINETICS Adrenaline is not suitable for oral administration because of its rapid inactivation in the GI mucosa and liver. Adrenaline can be given subcutaneously ( s.c. ). In anaphylactic shock, the absorption of s.c. adrenaline is very poor, hence given intramuscularly. In cardiac arrest, it is given intravenously. It does not cross the BBB; is rapidly metabolized by COMT and MAO and the metabolites are excreted in urine.

19. ADVERSE EFFECTS They are tachycardia, palpitation, headache, restlessness, tremor and rise in BP. The serious side effects are cerebral haemorrhage and cardiac arrhythmias . In high concentration, adrenaline may cause acute pulmonary oedema due to shift of blood from systemic to pulmonary circulation. Adrenaline is contraindicated in most of the cardiovascular diseases such as hypertension, angina, cardiac arrhythmias, CCF, etc. It should also be avoided in patients on beta-blockers because it may cause hypertensive crisis and cerebral haemorrhage due to unopposed action on vascular alpha 1-receptors .

20. USES OF ADRENALINE Anaphylactic shock bronchial asthma Cardiac resuscitation, hypotension Prolongs the Duration of local anaesthesia c ontrols Epistaxis and other capillary oozing

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