FOR U G STUDENTS

1. SYMPATHOMIMETICS
DR A G DHAVALSHANKH

2. INTRODUCTION
• CATECHOLAMINES: SYMPATHOMIMETICS WITH CATECHOL NUCLEUS ARE CALLED
CATECHOLAMINES THEY ARE AS FOLLOWS:
• ADRENALINE
• NORADRENALINE
• DOPAMINE
• ISOPRENALINE
• DOBUTAMINE

3. DOBUTAMINE
• RELATIVELY SELECTIVE BETA ONE AGONIST
• IT IS A SYNTHETIC CATECHOLAMINE STRUCTURALLY RESEMBLES DOPAMINE.
• IT ACTS ON BETA 1 BETA 2 AND ALPHA 1 RECEPTORS. IT IS A POTENT INOTROPIC
AGENT BUT CAUSES ONLY SLIGHT INCREASE IN HEART RATE .
• TOTAL PERIPHERAL RESISTANCE IS NOT SIGNIFICANTLY AFFECTED. THIS IS BECAUSE
VASOCONSTRICTION(ALPHA 1MEDIATED) IS BALANCED BY VASODILATION( BETA 2
MEDIATED).
• IT IS ADMINISTERED BY IV INFUSION IN PATIENTS WITH ACUTE HEART FAILURE. THE
SIDE EFFECTS ARE TACHYCARDIA AT HIGH DOSES RISE IN BP AND TOLERANCE WHICH
CAN BE AVOIDED BY INTERMITTENT THERAPY

4. ISOPRENALINE
• BETA 1 BETA 2 AND BETA 3 AGONIST
• IT IS A SYNTHETIC ,NON SELECTIVE BETA RECEPTOR AGONIST WITH A
CATECHOL NUCLEUS. IT HAS POTENT BETA ACTIONS BUT NO ACTION AT ALPHA
RECEPTOR.
• ISOPRENALINE IS A POWERFUL CARDIAC STIMULANT. IT HAS POSITIVE
INOTROPIC, CHRONOTROPIC AND DROMOTROPIC EFFECTS.
• IT DILATES RENAL , MESENTRIC AND SKELETAL MUSCLE BLOOD VESSELS.
• SYSTOLIC BP IS MINIMALLY CHANGED BUT THE DIASTOLIC AND MEAN ARTERIAL
PRESSURE IS REDUCED.

5. • IT RELAXES BRONCHIAL AND GI SMOOTH MUSCLES. ISOPRENALINE IS NOT
EFFECTIVE ORALLY BECAUSE OF EXTENSIVE FIRST PASS METABOLISM. IT CAN BE
GIVEN PARENTERALLY OR AS AN AEROSOL.
• IT IS METABOLIZED BY C O M T AND IS USED TO INCREASE THE HEART RATE IN
HEART BLOCK.
• IN BRONCHIAL ASTHMA, ISOPRENALINE HAS BEEN REPLACED BY SELECTIVE BETA
2 AGONIST. SIDE EFFECTS ARE TACHYCARDIA , PALPITATION ,CARDIAC
ARRHYTHMIA, ETC. DUE TO ITS POWERFUL CARDIAC STIMULANT EFFECT.

6. DOPAMINE
• ALPHA 1 ALPHA 2 BETA 1 AND D1 AGONIST WITH NA RELEASE.
• IT IS A IMMEDIATE METABOLIC PRECURSOR OF NA.IT ACTS ON DOPAMINERGIC D1
RECEPTORS AS WELL AS BETA 1 AND ALPHA 1 ADRENERGIC RECEPTORS.
• IT IS NOT EFFECTIVE ORALLY SO ADMINISTERED BY IV INFUSION AS IT IS RAPIDLY
INACTIVATED BY COMT AND MAO.
• PHARMACOLOGICAL ACTIONS:
1. AT LOW DOSES (2- 5MCG/KG/MIN), IT SELECTIVELY DILATES RENAL, MESENTRIC
AND CORONARY BLOOD VESSELS BY ACTING ON D1 RECEPTORS RESULTING IN
INCREASE IN GFR.

7. 2. AT MODERATE DOSES( 2-5MCG/KG/MIN), IT STIMULATES BETA
RECEPTORS OF HEART,INCREASES MYOCARDIAL CONTRACTILITY AND
CARDIAC OUTPUT, BUT TACHYCARDIA IS LESS PROMINENT. IT ALSO
STIMULATES DOPAMINERGIC RECEPTORS RESULTING IN INCREASE IN GFR
3. AT HIGH DOSES(>10MCG/KG/MIN), IT STIMULATES VASCULAR ALPHA
1 ADRENERGIC RECEPTORS AND CAUSES GENERALIZED
VASOCONSTRICTION. THIS INCRESES AFTERLOAD AND REDUCES BLOOD
FLOW TO RENAL, MESENTRIC AND OTHER VITAL ORGANS.SO,THE
BENEFICIAL EFFECT SEEN WITH LOW TO MODERATE DOSE OF DA IS LOST
AT HIGHER DOSES.

8. • PRECAUTIONS AND ADVERSE EFFECTS:
1. DURING DOPAMINE INFUSION THE DOSE BP HEART RATE ECG AND URINE
OUTPUT SHOULD BE MONITORED CAREFULLY
2. THE ADVERSE EFFECTS SEEN ARE MAINLY DUE TO SYMPATHETIC STIMULATION.
THEY ARE NAUSEA VOMITING HEADACHE HYPERTENSION TACHYCARDIA
CARDIAC ARRHYTHMIAS AND ANGINA.

9. • THERAPEUTIC USES
1. CARDIOGENIC AND SEPTIC SHOCK.
2. SEVERE HEART FAILURE WITH RENAL IMPAIRMENT.

10. THANKYOU