SPCP: HAI Cas Study (1) Flashcards
Class and MOA of omeprazole
PPI
Binds to H+/K+ ATPase transporters on gastric parietal cells and irreversibly inhibits their action therefore secretion of gastric acid. Pumps take ~24 hours to resynthesize therefore halts production for this time period. They are only effective when parietal cells are actively secreting so must bind during this time.
Class and MOA of Loperamide
anti-motility agent
Loperamide is an opiate receptor agonist that stimulates opiate receptors in the GI tract. Binding inhibits Ach & prostaglandin release which ultimately leads to a reduction in motility i.e reduction in peristalsis and increases intestinal transit time and enhances water reabsorption from the faeces.
Class and MOA of Dalteparin
Low Molecular Weight Heparin
Binds to Antithrombin III (ATIII) and potentiates its activity, inhibiting the formation to factor Xa and thrombin, inhibiting the clotting cascade.
Class and MOA of Co-amoxiclav
Penicillin antibiotic
Binds to Penicillin binding protein (PBPs) and inhibits bacterial cell wall peptidoglycan synthesis. It inhibits the enzymes that cross link peptide chains attaches to peptidoglycan. This results in weakened cell walls and osmotic cell lysis.
Clavulanic acid prevents beta-lactamases from breaking down the beta-lactam ring in amoxicillin.
Class and MOA of Trimethoprim
Sulfonamides antibiotic
Trimethoprim binds to dihydrofolate reductase and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the thymidine synthesis pathway, essential for pyrimidine and purine synthesis. It therefore interference with this pathway inhibits bacterial DNA synthesis.
Class and MOA of Vancomycin
Bactericidal antibiotic which inhibits bacterial cell wall synthesis. In addition, it impairs the permeability of bacterical cell membrane and RNA synthesis.
Class and MOA of Dioralyte
(rehydration salt)
The combination of electrolytes stimulates water and electrolyte absorption from the GI tract.
Class and MOA of Erythromycin
(Macrolide Antibiotic)
Bacteriostatic antibiotic that inhibits growth of bacteria. It binds to a specific site on the 50S ribosomal subunit and binding stimulates premature dissociation of peptidyl tRNA from ribosomes during protein synthesis.
Class and MOA of Famotidine
(Histamine 2 Receptor antagonist)
Reversibily binds to H2 receptors on gastric parietal cells, blocking Histamine release. Histamine normally stimulates gastric acid production therefore this reduces gastric acid secretion.
Pharmacokinetics of Omeprazole
A: Rapid absorption from the small intestine with peak plasma levels occurring ~1-2hr after dose
D: Vd ~ 0.3L/kg and 97% protein bound
M: Completely metabolised by CYP450. Metabolism by CYP 2C19 forms the major metabolite. Other CYP450’s are CYP3A4.
E: ~80% excreted as metabolites in urine and remainder in faeces
Pharmacokinetics of Loperamide
A: Most absorbed from the GUT, but due to significant FPM, systemic BA is only 0.3%
D: Plasma protein binding is 95% - mainly albumin
M: loperamide is almost completely extracted by the liver, where it is predominantly metabolized, conjugated and excreted via the bile. Oxidative N- demethylation is the main metabolic pathway for loperamide, and is mediated mainly through CYP3A4 and CYP2C8. Due to this very high first pass effect, plasma concentrations of unchanged drug remain extremely low.
E: The half-life of loperamide in man is about 11 hours. Excretion of the unchanged loperamide and the metabolites mainly occurs through the faeces.
Pharmacokinetics of Dalteparin (SC)
Half-life ~3.5-4h. BA ~87%. PK not dose dependent. Mainly excreted through kidneys
Pharmacokinetics of Co-amoxiclav
A: Amoxicillin & Clavulanic acid are quickly and well absorbed. Absorption is optimized if taken at start of meal.
D: C 25% PPB & Amx 18% PBM. Both pass into placenta and A can pass into breast milk.
M: C extensively metabolized and Amx partly excreted as inactive form.
E: Amx major route is kidneys and C is by renal and non-renal mechanisms.
Pharmacokinetics of Trimethoprim
A: Rapidly and almost completely absorbed from GIT. Peak conc 1-4hr after admin.
D: ~40-70% PPB. Tissue concentration greater than seum, which especially high in kidneys and lungs. Half-life ~8-10h.
M & E: ~40-60% excreted unchanged in urine with metabolites – may need dose reduction in elderly.
Pharmacokinetics of Vancomycin
A: Not usually absorbed into bloodstream after oral administration.
E: Mostly excreted in faeces
Pharmacokinetics of Erythromycin
A: Absorbed from small intestine. Peak levels ~1h.
D: Widely distributed
M: little metabolism. Elimination half-life ~2h.
E: Primarily liver excretion
Omeprazole:
- Indication
- C/I
- Cautions
- Interactions
- Side-effects
Indications:
• H.pylori eradication
• Gastric or duodenal ulceration
• Prevention of relapse in gastric or duodenal ulcer
• NSAID-associated duodenal/gastric ulcer
• Gastro-oesophageal reflux disease
• Acid-reflux disease (long-term management)
C/I: Hypersensitivity to active substance or excipients, not used with nelfinavir
Cautions:
• Risk of osteoporosis, gastric cancer, elderly
• Avoid stopping abruptly – rebound acid-hypersecretoin.
Interactions:
• inhibits CYP2C19:
o Clopidogrel, Warfarin, Diazepam
• Increase gastric pH - interferes with the solubility of medicines that require acidic pH:
o Epclusa (Hepatitis C)
o Itraconazole capsules
o Erlotinib (EGFR inhibitor for lung/pancreatic cancer)
• Cumulative effect with medicines that cause low Na+ and Mg2+
Side effects: Ab pain, constipation, diarrhea, dizziness, dry mouth, Insomnia, nausea, headache
Loperamide
- Indication
- C/I
- Cautions
- Interactions
- Side-effects
Indication: Diarrhoea
ADR:
• Gastrointestinal disorders; headache; nausea
Caution:
• Under 12
C/I:
• Active ulcerative colitis; antibiotic-associated colitis; bacterial enterocolitis; conditions where abdominal distension develops; conditions where inhibition of peristalsis should be avoided
Interactions:
• EMC/BNF
Method of administration:
• Tablet, Orodispersible tablet, Capsule, Oral solution
Dalteparin
- Indication
- C/I
- Cautions
- Interactions
- Side-effects
Indication:
C/I: Peptic ulcer, thrombocytopenia, acute bacteria endocarditis, mechanical prosthetic heart valve
Cautions: Elderly, risk of bleeding, severe hypertension
Side-effects: skin reactions, haemorrhage, herparin-induced thrombocytopenia, hyperkalaeia
Interactions:
• NSAIDs, vitamin K antagonsist – enhance anticoagulantion effect
• Cardiac glycosides, antihistamines, tetracycline – reduce anticoagulation effect
Co-Amoxiclav
- Indication
- C/I
- Cautions
- Interactions
- Side-effects
Indication: Effective against gram +ve and –ve bacteria (more effective against +ve)
C/I: co-amox/ penicillin associated jaundice or hepatic dysfunction, severe hypersensitivity reaction to B-lactam.
Cautions: lymphocytic leukaemia, cytomegalovirus, glandular fever.
Side-effects: diarrhea, hypersensitivity, nausea, skin reactions, thrombocytopenia, increases risk of infections
Interactions:
• Oral anticoagulants – some cases of increased IRN on warfarin – may need oral anticoagulant dose adjust.
• Mxt – reduce Mxt excretion which can cause toxicity
•
Patient-Specific Factors:
• Risk of crystalluria with high doses
