GORD/PUD Flashcards
Name 4 classes of drugs used to treat GORD/PUD?
- NSAIDs
- PPIs
- Histamine (H2) receptor antagonsits
- Paracetamol (acetaminophen)
Give some examples of NSAIDs
- Ibuprofen
- Naproxen
- Diclofenac
- Aspirin
Give some examples of PPIs
- Omeprazole
- Lansoprazole
Give an example of a H2 receptor antagonists
Ranitidine
What is the primary mechanism
of action for NSAIDs?
- Inhibit the cyclo-oxygenase (COX) which is the rate-limiting step for the production of all prostanoids (prostaglandins and thromboxanes) from the parent arachidonic acid
- It’s thought that the anti-inflammatory actions and probably most of the analgesic and antipyretic actions of the NSAIDs are related to inhibition of COX-2 while their unwanted effects are largely a result of inhibition of COX-1
What is the primary mechanism
of action for PPIs?
- Pro-drugs that are irreversible inhibitors of H+/K+ ATPase (proton pump) on the apical membrane of gastric parietal cells (so they transport protons out of parietal cells)
- They are weak bases and accumulate in the acid environment of the canaliculi of the parietal cells which concentrates their actions there and prolongs their duration of action
What is the primary mechanism
of action for H2 receptor antagonists?
Competitive antagonists of H2 receptors (structural analogues of histamine) which inhibit the stimulatory action of histamine released from enterochromaffin-like (ECL) cells on the basolateral membrane of gastric parietal cells
What is the primary mechanism
of action for paracetamol?
- Actions appear to be largely restricted to nervous tissue but its mechanism is unclear
- Currently thought to have a central and peripheral action involving interaction w/ a COX-3 isoform (inhibits PG synthesis)
- Inhibits reuptake of endogenous endocannabinoids by binding to cannabinoid reuptake proteins which would increase activation of cannabinoid receptors or endogenous opioids
- Activation of descending serotonergic pathways possibly via 5HT3 receptor activation & adenosine receptors have also been proposed
What are some side effects of NSAIDs?
- Gastric irritation, ulceration and bleeding and in extreme cases, perforation
- Reduced creatinine clearance and possible nephritis
- Bronchoconstriction in susceptible individuals (contraindicated in asthma)
- Skin rashes and other allergies
- Dizziness
- Tinnitus
- Adverse CV effects (hypertension, stroke, MI) may occur following prolonged use or in patients with pre-existing CV risk
- Prolonged analgesic abuse -> chronic renal failure
- Aspirin -> post-viral encephalitis (Reye’s syndrome) in children
What are some side effects of PPIs?
- Headache, diarrhoea, bloating, abdominal pain and rashes
- The use of these drugs may mask the symptoms of gastric cancer
- Omeprazole is an inhibitor of cytochrome P2C19 and has been reported to reduce the activity of drugs e.g. clopidogrel
What are some side effects of H2 receptor antagonists?
- Diarrhoea, dizziness, muscle pains & transient rashes have been reported
- Cimetidine (but not other H2 antagonists) inhibits cytochrome P450 and may slow metabolism and potentiate the effects of drugs e.g. oral anticoagulants and TCAs
What are some side effects of paracetamol?
- Doesn’t cause gastric irritation but in overdose serious hepatotoxicity or renal damage may occur, nausea and vomiting are early features of poisoning and right subcostal pain after 24hrs indicates hepatic necrosis
- Occasional allergic skin reactions
