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Ergot Alkaloids Dr. Naila Abrar
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LEARNING OBJECTIVES After this session, you should be able to: know the source and classification of ergot alkaloids; describe pharmacological actions of ergot alkaloids; comprehend the clinical indications of ergot alkaloids; and describe the adverse effects & contraindications of ergot alkaloids.
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SOURCE: SOURCE: fungus - Claviceps purpureaDISCOVERY:ERGOTISM: St. Anthony’s fire
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Claviceps purpurea
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CLASSIFICATION AMINE ALKALOIDS 6- Methylergoline, lysergic acid, lysergic acid diethylamide, ergometrine (ergonovine), methysergide PEPTIDE ALKALOIDS Ergotamine, dihydroergotamine, - ergocryptine, bromocriptine
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CHEMISTRY Ergoline nucleus Derivatives of tetracyclic compound 6- methylergoline Substituent in beta configuration at position 8 and a double bond in ring D Natural alkaloids: ergotamine, ergonovine (derivatives of d-lysergic acid) Semisynthetic & synthetic: dihydroergotamine, bromocriptine, LSD, methysergide
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PHARMACOKINETICS Variable absorption from GIT Ergotamine- poor oral BA Speed of absorption and peak blood levels of ergotamine improved with caffeine Routes: oral S/L, I/M, I/V, nasal, rectal Extensive metabolism Ergonovine & methylergonovine - rapidly absorbed
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MECHANISM OF ACTION Multi-receptor function Agonist, partial agonist, and antagonist at , serotonin Presynaptic 5HT receptor (5HT 1A/1D ) Partial agonist at 5HT 2 - uterus Partial agonist at CNS dopamine Antagonist at blood vessels dopamine
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PHARMACOLOGICAL ACTIONS CNS Hallucinogenic LSD – drug abuse (agonist at 5HT 2 in CNS) Nausea, vomiting – CTZ D 2 Decrease extrapyramidal symptoms - striatum D 2 Inhibition of prolactin secretion – pituitary D 2 Bromocriptine, pergolide, cabergoline
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VASCULAR SMOOTH MUSCLE stimulation – VC – increase TPR & BP Also vascular 5HT 2 Ergotamine- partial agonist Vasospasm Flow of blood to periphery decreases Slow dissociation from receptors
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UTERUS Stimulation of & 5HT 2 More in uterus at term Ergonovine (ergometrine) more selective Rhythmic contractions and relaxation in small doses and prolonged contracture at higher doses
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GIT Stimulation of 5HT 2 receptors Increase motility, diarrhea, abdominal cramps Dopamine receptors CTZ – anorexia, nausea, vomiting
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CLINICAL USES MIGRAINE Triptan drugs Prodrome of attack – ergotamine tartrate Increase absorption with caffeine S/L 2 mg half hourly till relief - No more than 6mg for each attack or no more than 10mg /wk 0.25-0.5mg I/V or I/M total dose of 2 -3mg in 24hrs 0.5 mg nasal spray- repeated after 15 mins if req. total dose of 2 mg in 24hrs
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HYPERPROLACTINEMIA Bromocriptine, cabergoline, pergolide PARKINSONISM Bromocriptine, decrease EP effects POST PARTUM HEMORRHAGE Ergonovine maleate 0.2 mg I/M DIAGNOSIS OF VARIANT ANGINA Ergonovine to localize reactive segments of coronaries during angiography SENILE CEREBRAL INSUFFICIENCY Alzheimer’s disease
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ADVERSE EFFECTS GIT: GIT: NVD, abdominal cramps VASOSPASM: VASOSPASM: Severe, gangrene CNS: CNS: Hallucinations, delirium, mania, drowsiness, sedation, drugs of abuse - LSD RETROPERITONEAL FIBROSIS: RETROPERITONEAL FIBROSIS: Methysergide ERYTHROMELALGIA: ERYTHROMELALGIA: with ergot derived dopamine agonists like pergolide BP: BP: Raised UTERUS: UTERUS: Abortion
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Erythromelalgia
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CONTRAINDICATIONS Pregnancy Renal disease Hepatic disease Psychotic illness Collagen diseases Peripheral Vascular disease
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