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Antacids, anti-emetics &GI motility drugs
Dr Ally DuncanEducation Fellow & SpR in AnaestheticsManchester Royal Infirmary
April 2012
Applied Sciences LectureCourse
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Aims and objectives
Categorise drugs acting on the gut
Discuss relevant pharmacologicalaspects
Discuss common clinical uses
Categorise antiemetics
Discuss relevant pharmacologicalaspects
Discuss common clinical uses
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Drugs acting on the gut
Antacids
Drugs influencing gastric secretion
Drugs influencing gastric motility
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Antacids
Drug action based on physicalproperties
Weak bases that neutralise gastricacid
Traditionally compounds containingaluminium or magnesium
Liquid more effective than tablet
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Antacids
Clinical uses:
symptomatic relief of dyspepsia
some promotion of ulcer healing but
less effective than drugs that inhibitacid secretion
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Antacids
Magnesium containing
Laxative
Aluminium containing Constipating
Interactions May affect absorption of other drugs.
Avoid giving at same time
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Antacids
Examples Aluminium hydroxide
Magnesium trisilicate
Over the counter Gaviscon
Sodium alginate, sodium bicarbonate, calcium chloride
Peptac Sodium alginate, calcium carbonate
Rennie Duo Calcium carbonate, magnesium carbonate
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Drugs influencing gastricsecretion
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Mechanism of gastric acidsecretion
Gastrin AcetylcholinePGE2Histamin
H+
K+
ATP-ase
Ca2
+
Ca2
+
Gs Ac Gi
Protein Kinases
ATPCyclicAMP
ParietalCell
Apical Cellsurface
H2
receptor
Muscarinicreceptor
Proton pump
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Drugs influencing gastricsecretion
H2 receptor antagonists
Proton pump inhibitors
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H2 receptor antagonists
Reduce basal and food stimulatedgastric acid by 90%
Heal gastric and duodenal ulcers
Provide symptomatic relief indyspepsia
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Which of the following is notan H2 antagonist?
1 2 3 4 5
0%
17%
0%
50%
33%
1. Ranitidine
2. Zantac
3. Gavilast4. Losec
5. Cimetidine
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H2 receptor antagonists
Rantidine
Zantac, gavilast
Oral / IV preparations
Available over the counter
Side effects (rare)
Cardiac arrhythmias during rapid IV
administrationThrombocytopenia, leucopenia, liver
dysfunction
Anaphylaxis
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H2 receptor antagonists
Cimetidine
Hepatic enzyme inhibitor (AODEVICES)
Inhibits cytochrome P450 system
Can reduce metabolism of other drugscausing a rise in serum levels e.g.warfarin
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Enzyme INHIBITORS
A Allopurinol
O Omeprazole
D Disulfiram
E Erythromycin V Valproate
I Isoniazid
C Cimetidine & ciprofloxacin E Ethanol (acute intoxication)
S Sulphonamides
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Enzyme INDUCERS
P Phenytoin
C Carbamazepine
B Barbiturates R Rifampicin
A Alcohol
S Sulphonylureas
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Proton pump inhibitors
Cause irreversible inhibition of proton pump Final common pathway of gastric acid production
Examples Esomeprazole
Nexium Lanzoprazole
Zoton
Omeprazole Losec
Pantoprazole Protium
Rabeprazole pariet
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Proton pump inhibitors
Uses
Dyspepsia & GORD
Treatment of gastric & duodenal ulcers
H. pylori eradication
In combination with antibacterials
Bleeding peptic ulcers (IV)
To reduce further bleeding & need forsurgery
Zollinger-Ellison syndrome
Gastrin producing tumour
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Proton pump inhibitors
Side effects
Inhibition of cytochrome p450 system
Limited. Rarely substantial effect
Rarely rashes & GI disturbances
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Drugs influencing gastricmotility
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Drugs influencing gastricmotility
Reduce motility Antispasmodics Antimotility drugs
Codeine
Loperamide
Increase motility Prokinetics
Laxatives Bowel cleansing solutions
Picolax Klean-prep
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Antispasmodics
Antimuscarinics
Hyoscine butlybromide
Buscopan
Uses
Symptomatic relief of gastro-intestinal orgenito-urinary disorders characterised bysmooth muscle spasm
IBS
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Antispasmodics
Other
Mebeverine
Peppermint oil
Thought to be direct relaxants of intestinalsmooth muscle
May relieve pain & diverticular disease
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Prokinetics
Drugs which stimulategastrointestinal motility
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Which of the following is notconsidered a prokinetic?
1 2 3 4
30%
0%
70%
0%
1. Loperamide
2. Metoclopramide
3. Erythromycin4. Domperidone
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Prokinetics
Dopamine antagonists
Stimulate gastric emptying and small intestinaltransit
Examples Metoclopramide
Domperidone
Uses
Functional dyspepsia GORD
Gastroparesis in diabetes
Aid speed of transit of barium in follow through test
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Prokinetics
Erythromycin
Increases gastric & small bowel activity
Thought to act on motilin receptor
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Laxatives
Bulk-forming Isaghula Husk
Fybogel
Stimulant Docusate sodium
Senna
Glycerol suppositories
Osmotic Lactulose
Movicol
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Anti-emetics
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Vomiting
Afferent pathway
Control centre
Efferent pathway
Vagus nerve Phrenic nerve
Spinal motor neurones supplying abdo muscles
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Vomiting
Chemoreceptor Trigger Zone(Area Postrema, floor of 4th ventricle)
Outside BBB
5HT
3D
2
Dopamine Drugs Gut
Gut
Vestibular apparatus& cerebellar nuclei
Peripheral painpathways
Chemoreceptors &baroreceptors
VomitingCentremedulla
H
1
ACh
5HT
3
Limbic cortex
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Which group IS NOT used as anantiemetic?
1 2 3 4 5
9%4%
87%
0%0%
1. Antihistamine
2. Antimuscarinics
3. Dopaminergicantagonists
4. 5-HT3 receptor
antagonists5. Opioids
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Antiemetics
Dopamine Antagonists
Antihistaminines
Antimuscarinics
5HT3 receptor antagonists
miscellaneous
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Dopamine antagonists
Metoclopramide
Phenothiazines
Prochlorperazine (Stemetil)
Chlorpromazine
Thoridazine
Domperidone
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Dopamine antagonists
Side effects
Extrapyramidal side effects
Acute dytonias, ocular gyric crises
Commoner in young women
Can trigger neuroleptic malignant syndrome
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Antihistamines
Cyclizine
Also has anticholinergic properties
Side effects
Pain on injection
Tachycardia (IV bolus)
Antimuscarinic effects
Dry mouth, blurred vision
Restlessness, excitation, nervousness
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Antimuscarinics
Hyoscine hydrobromide
Particularly effective in motion sickness
Atropine
Glycopyrrolate
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5HT3 Antagonists
Ondansetron
Dolasetron
Granisetron
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Miscellaneous
Corticosteroids
Dexamethasone
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Vomiting
Chemoreceptor Trigger Zone(Area Postrema, floor of 4th ventricle)
Outside BBB
5HT
3D
2
Dopamine Drugs Gut
Gut
Vestibular apparatus& cerebellar nuclei
Peripheral painpathways
Chemoreceptors &baroreceptors
VomitingCentremedulla
H
1
ACh
5HT
3
Limbic cortex
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Commonest Antiemetics used inHospital
Prochlorperazine (stemetil)
12.5mg IM
3mg Buccal (Buccastem)
Cyclizine
50mg PO/IM/IV
Metoclopramide
10mg PO/IM/IV
Ondansetron
4-8mg PO/IM/IV
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Summary
Discussed Drugs affecting the GItract
Antacids
Drugs inhibiting acid secretion
Antispasmodics
Prokinetics
Laxatives
Discussed antiemetics
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Any questions?