22) GI pharmacology Flashcards
Outline the features of GORD > What it is > Symptoms > Complications > Risk Factors > Management
Symptoms or complications resulting from the reflux of gastric contents into the oesophagus or beyond
Symptoms:
> Heart burn, Cough, Laryngitis, Asthma, Dental Erosion
Complications: > Oesophagitis > Ulceration > Haemorrhage > Stricture formation > Barrett's Oesophagus
Risk Factors:
> Elderly, Hiatus hernia, Obesity, Pregnancy, Smoking, Alcohol
Management:
Lifestyle => Reduce / Stop medications that exacerbate GORD ; Weight Loss ; Avoiding Trigger foods; Smaller meals ; Eating Earlier ; Alcohol and Smoking
Drug Rx => PPIs , if it doesn’t work add Histamine Receptor Antagonist (H2RA)
OR Fundoplication
Outline the features of Gastritis > What it is > Symptoms > Complications > Risk Factors > Management
Inflammatory Changes to Gastric Mucosa
Sx:
> Burning Epigastric Pain, Nausea and Vomiting
Complications:
> GI Tract Bleeding
Risk Factors:
> H pylori Infection, Chronic NSAID use, Bile Reflux
Management:
Erosive => NSAIDs, Alcohol, Bile
- Reduce / Stop irritants
- PPI or H2 RA
Non Erosive => H pylori
- Triple Therapy => PPI + 2 ABx (Amoxicillin + Clarithromycin + Metronidazole)
Autoimmune
- Cyanocbalamin
Outline the Characteristics of Peptic Ulcer Disease > What it is > Symptoms > Complications > Risk Factors > Management
Defects in the gastric or duodenal mucosa that exten through the muscularis mucosa
Sx:
> Epigastric Pain after meals
Complications:
> Perforation => Peritonitis
Risk Factors:
> H Pylori, NSAIDs
Management: Eliminate underlying cause, Relieve Sx, Heal ulcers and treat complications
H Pylori -ve => Stop NSAIDs , PPI / H2 RA if unresponsive
H pylori +Ve => Eradicate regime
Outline the different types of Mucosal Defence
Epithelia - There are stem cells found in the crypts which constantly regenerate to restore the epithelia to provide a barrier against acid
Mucus - Alkaline barrier against acidic environment ; Lubricates to reduce physical damage ; Traps bacteria
Acid - Reduce bacteria invasion
Vascular Supply - Good
Prostaglandin - PGE2 and PGI2 > Potent vasodilators > Decrease Acid Secretion > Stimulate Mucus and bicarb secretion in stomach Effects: - Reduced permeability of epithelium to back flow acid - Reduce Inflammatory Mediators - Promote Ulcer Healing
Outline the characteristics of Proton Pump Inhibitors > Examples > Mechanism of Action > Metabolism > Side Effects > Interactions
Omeprazole, Lansoprazole
> Pro drugs
MOA:
> Bind covalently to Gastric H+ on parietal cells , K+ ATPase irreversibly and block function => Prolonged and near complete suppression of acid secretion
Metabolism:
> By CYP450
Side Effects: Usually well tolerated > Headache > Nausea > GI tract Issues > Abdo pain
Interactions:
> May affect effectiveness of Clopidogrel since then by use CYP2C19
Outline the Characteristics of Histamine Receptor Antagonists > Examples > Mechanism of Action > Metabolism > Side Effects
Rantidine
MOA:
> Competitively and Reversibly binds to H2 Receptors
- Indirectly blocks the effect of Gastrin and Ach on the Parietal cells
Metabolism:
> Liver and excreted by kidney
Side Effects: > Diarrhoea > Constipation > Muscle Ache > Fatigue
Outline the characteristics of Prostaglandin Analogues > Examples > Mechanism of Action > Side Effects > Contraindications / Indication
MOA:
> Acts on PGE2
Side Effects:
> Diarrhoea
> Abdominal Pain
Contraindications:
> Pregnant women
- Causes Uterine Contractions
Indications:
> Treatment of NSAID induced Ulcers
Outline the Characteristics of Antacids
> Examples
> Mechanism of Action
> Different preparations and Side effects
Symptom relief for dyspepsia
MOA:
> Neutralises HCl, reacts with water to from water and salt
Aluminium Hydroxide:
> Constipation
> bind to phosphate => Low phosphate ( Weakness, Malaise)
> In renal failure neurotoxicity
Magnesium Hydroxide
> Diarrhoea
> Avoid in renal failure
Sodium Bicarbonate
> Avoid in Hypertension and Fluid Overload and it forms water and salt
Calcium Carbonate
Outline Step up and Down therapy when treating GORD ?
Start patients on H2 RA then PPI if necessary (Up)
Start patients on PPIs then H2 RA to maintain
Describe the transformation of parietal cells from resting to secreting
in resting state proton pumps are located in membrane bound compartment (Tubulovesicles) - Lacking K+ permeability blocking H+ / K ATPase activity
Apical membrane of Parietal cells has K+ Channels and Involutions (Canaliculi)
Tubulovesicles and Canaliculi fuse and so Proton pumps can exchange H+ for K+
