GI Drugs Flashcards
Name PPIs
Omepraziole
Lansoprazole
Pantoprazole
Indications of PPIs
1) Duodenal and gastric ulcers
2) Eradicating H. Pylori - in combination with antibitoics
3) Zollinger-Ellison Syndrome
4) GORD
5) Stircturing and erosive oesophagitis
What is Zollinger-Ellison syndrome?
A rare condition in which one or more tumours forms in the pancreas or the duodenum
These tumours secrete lots of gastrin - a hormone that causes your stomach to produce too much acid
Side effects of PPIs
Headache, diarrhoea, abdo pain (most common)
Nausea, flatulence, dry mouth (less common)
Managing the adverse effects of PPIs
Side effecst usually mild
Analgesia for headache
Report excessive diarrhoea
Action of PPIs
Inhibit gastric acid by blocking H+/K+ enzyme of the gastric parietal cell
Contraindications of PPIs
Hypersensitivity
Pregnancy and lactation
Caution in older adults and patients with liver disease
Interactions of PPIs
1) Omeprazole inhibits cytochrome P450
2) Lansoprazole is a weak inducer of cytochrome P450
Omeprazole and clarithromycin –> increased serum concentration of both drugs
Name some antacids
Gaviscon
Indications of antacids
1) Hyperaciditiy problems e.g. Heartburn GORD Sour Stomach Peptic Ulcers
What are the 4 types of antacids
1) Aluminium
2) Calcium
3) Magnesium
4) Sodium Carbonate
What is the additional use of aluminium antacids
It treats hyperphosphataemia
Adverse effects of each type of antacids
Aluminium - constipation, intestinal impaction
Calcium - rebound hyperacidity
Magneisum - severe diarrhoea
Sodium Carbonate - Systemic Alkalosis
Contraindication of antacids
Severe abdominal pain with no known cause
During lactation
Na: Patients with CV problems e.g. hypertesnion
Ca: Patients with renal calculi or hypercalcaemia
Al: Gastric outlet obstructions
Mg + Al: Decreased kidney function
Side effecst of antacids
Magnesium and Sodium = diarrhoea
Aluminium and calcium = constipation
Interactions of antacids
1) They increase gastric pH - hence reduce the absorption of weakly acidic drugs
2) Absorbs/binds to drug surface - decrases the absorption of tetracycline
3) Increases urinary pH changing the rate of drug elimination
4) Decreases pharmacological effect of: corticosteroids, Iron, digoxin, chlorpromazine, ranitidine, tetracyclines, isonizaid
Name H2 antagonists
Ranitidine/Zantac
Cimetidine/Tagamet
Nizatadine + Famotidine/ Pepcid
Indications of H2 antagonists
Gastric + duodenal ulcers
Gastric hypersecretion + GORD
Prevent stress related ulcers
Adverse reactions of H2 antagonists
Dizziness Somnolence Headache Confusions Hallucinations Diarrhoea Impotence
Managing adverse reactions of H2 antagonists
Most are mild and transient
May requied help with walking/self care
Skin rash, fever, bleeding, hallucinations should be reported immediately
Actions of H2 antagonists
Inhibit histamine action at stomach
Reduces gastric acid secretion
Reduces total pepsion
Decreased acid allows gastric ulcers to heal
Contraindications of H2 antagonists
Hypersensitivity
Renal/hepatic impairment
Caution in older people due to causing confusion
Caution in pregnancy and lactation
Interactions
1) Antacids + metoclopramide decreases if concurrent
2) Cimetidine + digoxin: causes low digoxin levels
3) Alkylating drug or antimetabolite - causes low WBC
4) Cimetidine + morphine: Increased risk of respiratory depression
5) Increased toxicity of oral anticoagulants, phenytoin, lidocaine, quindine, theophylline
Name amino-salicylates
Mesalazine/Asacol
Sulfasalazine
Anti-inflammatories
Indications of amino-salicylates
1) Mild/moderate UC - helps prevent further episodes
2) Maintenance of remission of Crohn’s ileocolitis
Contraindications
Allergy Decreased kidney function Decreased liver function Blood clotting abnormalities Chilren under 12 Avoid sulfasalazine in G6PD deficiency + men who want to stay fertile
Side effects
Nausea Abdo Pain Vomiting Diarrhoea Dizziness Flatulence Headache Rashes (including toxic dermal necrolysis)
Action of amino-salicylates
Readily absorbed from the small intestine - attached to a resin to ensure release in the large bowel
Act on cells lining the small and large intestine - changes the way they release chemicals (stops UC)
Mesalazine blocks COX + inhibits prostaglandin production in action - allowed damaged intesting to occur
Interatcions of aminosalicylates
1) Indigestion remedies - can affectt ablet coating preventing mesalazine elease
2) Lactulase medication altering stool pH - prevent mesalazine wokring
3) Risk when used with azathioprine/mercaptopurine –> increased risk of side effects on blood cells
eliminations of aminosalicylates
Faeces
Name some laxatives
Senokot
Movicol
What are the 4 different types of laxatives
1) Bulking agents
2) Stool softeners
3) Osmotic laxatives
4) Stimulant laxatives
How do bulking agent laxatives work
Absorb mor fluid
Bigger stools
Gives you the urge to pass stool
Works in 12-24 hours
How do stool softener laxatives work
Soften the stool
Easier to pass
Only work if you drink enough water
WOrk in 24-48 hours
How do osmotic laxatives work
These are things such as milk/lactulose
Holds fluid in the intestine
Draws fluid into the intesting form the tissues
Makes the stool softer and easier to pass
Works in up to 2 days
How do stimulant laxatives work
E.g. Dulcolax and Senokot
SPeeds up stool through the intestine by stimulation the nerve
Regular use not recommended as this changes the tone and feeling in the large intesting and can leed to dependences
They work in 8-12 hours
What type of laxative is movicol
An osmotic laxative
Contraindication of laxatives
Bowel obstructoin
Crohns/UC
Side effects of laxatives
1) Osteopenia - regular use changes ability to absorb vitamin D/calcium
2) Bulk forming lacatives –> can make symtpoms worse is you have severe constipation = abdo bloating and discomfort without clearing faeces that are further downt he gut
Interactiosn of laxatives
Antacids containing Aluminum or magnesium
What order should you prescribe laxatives
Bulk 1st line –> then osmotic –> then stimulant
Take any laxative with lots of water
How should patient take amino-salicylates
Take tablets whole with lots of water
Name some anti-diarrhoeal agents
Loperamide (immodium)
Atropine (Motofen)
Diphenoxylate with atropine (Lomotol)
Indications
Treats diarrhoea
Adverse reactions of anti-diarrhoead agents
Unusual for loperamide but include: Dry mouth skin rash Dizziness Abdominal Discomfort
Advesre reactins of diphenoxylate (Lomotil) anti-diarrhoea agent
It is a narcotic rlaeted drug
It has sedative and euphoric effects
It is commbined with atropine to discourge its abuse
What is atropine
Atropine is an anti-cholinergic drug
The side effects of this mean its combined with diphenoxylate
Managing the adverse reaction of anti-diarrhoeal agents
Monitor fluid intake/outtake
Replace electrolytes in severe diarrhoea
Mild soap for perianal irritaiton
What are the actions of anti-diarrhoeal agents
They decrease intestinal persitalsis
Potentially antagoniszing ACh release in the intramural nuerve plexus
They are poorly absorbed and act directly on the bowel
Contraindications of anti-diarrhoeal agents
Diarrhoea associated with organisms that can harm the intestinal mucosa (e.g. E. Coli, Shigella, Salmonella)
Pseudomembranous Colitis
Under 2 years age
Caution in using anti-diarrhoeal agents
Pregnancy + lactation
IBD
Severe liver disease
Interactinos of anti-diarrhoeal agents
Additive CNS depression with alcohol
Additive cholinergic effects when other drugs have antihcholinergic properties (e.g. antihistamine/depressants)
With monoamine oxidase inhibitors - increased hypertesive crisis
Is vomiting a somatic or autonomic response
It is somatic
Dopamine excites the CTZ - the CTZ activates the vomiting centre causing = emesis
ONLY USE ANTIEMETICS WHEN THE CAUSE OF COMITING IS KNOWN
Several types of anti-emetics
1) Antichonlinergics
2) Antihistamines
3) Dopamine antagonists
4) Phenothiazine
5) Neuroinine antagonists
6) Cannabinoids
7) 5-hydroxytryptamine receptor antagonists
What is hyoscine
an anticholinergic anti-emetic
What is promethiazine
an antihistamine anti-emetic
What is metoclopramine
a dopamine agonist anti-emetic
what is prochlorperazine
a phenzothiazine anti-emetic
What is aprepitant
A neurokinen antagonist anti-emetic
What is nabilone
A cannabinoid anti-emetic
What is ondansetron
What is 5-hydroxytryptamine receptor antagonist anti-emetic
Indications fo anti-muscarininc anti-emetics e.g. hyoscine
1) Motion sickness - useful in single doses. Its side ffects make it inappropriate for long term use
it is also an alternative to anti-histaimnes and phenothiazines for the treatment of vertigo and nausea associated with Meniere’s disease
Side effcts of anti0muscaring anti-emetic e.g. hyoscine
Drowsiness
Dry mouth
Blurred vision
Urinary retention
Indications of dopamine antagonists anti-emetic e.g. metaclopramide
Post-op nausea
Radiationi sickness
Allows diagnostic radiology of small intestine
Adverse effects of dopamine antagonist anti-emetics e.g. metaclopramide
Usually mild - but more common in women and young people
Extra-pyramidal effects (1%) Akathisia - movement disorder Oculogenic crises Torticolis - a crick in the neck Opisthontons - spasm of muscles Parkinsonian features
Treat with benzothriopine or diazepam
Action of dopamine antagonist anti-emetics
They increase ACh at post-ganglionic terminals
Central dopamine antagonist
Incrased doses block 5-HT3 receptor (serotonin receptors)
Pharacokinetcs of dopamine antagonists anti-emetics
Well absorbed orally
75% excreted as metablites in urine
Half life is 4 hours
Drug interactions of dopamine antagonists anti-emetics
Metacloprimade potentiates extra-pyramidal effects of phenzothiazines butryruptenes
Increase absorption of tetracyclines, aspirin, paracetamol
How does domperidone a dopamine receptors agaonists differ from metocloparmide
It doesn’t cross the BBB
Seldom causes extra-pyramidal effects
It can be given with levodopa to counter their emetogenic effect
How do phenothiazine anti-emetics work
Act on thte CTZ
useful against radiaiton-induced vomiting
Least effective against motion sickness
Risk of extra-pyramidal effects e.g. dyskinesia and restlessness
How do 5HT3 receptor antagonist anti-emetics work e.g. ondansetron
Treat acute nausea due to chemo or post op
Their site of action is unclear
How do cannabinoid anti-emetics e.g. nabilone work
Prevent vomiting due to cytotxic therapy
Acts on cortical centrea affecting descending vomiting pathways
Adverse effects of anti-emetics
Sedation Confusion Hypotension Loss of coordination Dry mouth
Indiciations of anti-histaminic anti-emetics
Motion sickness
Vertigo due to labyrinthe disroders
They also have additional anticholinergic effects
Limitations of anti-histaminic anti-emetics
modest efficicay and common dose related side effects
Antimuscarainic effects may be caused
When to use cyclisine
oral or injection for opiate-induced vomiting
Safe in prgancny
Which antihistamine anti-emetic is more sedative
Promethazine
What antihistamine anti-emetic should we use in vertigo
Betahistine
Also treates Meniere’s and hearing loss
what is Clinnazine
An Antihistamine and calcium antagonist anti-emetic
acts on the labyrinthe to treat motion sickness and vertigo
Name some miscellaneous anti-emetics
1) Glucocorticosteroids –> anti-emetic when with cytotoxic therapy as dexamethasone improves 5HT3 antagonists
2) Benzodiazpines –> give before cytotoxic treatment to reduce vomiting
