Drugs Flashcards
Describe first pass metabolism.
Fraction of a drug lost during the process of absorption in the gut and metabolism in the liver. Concentration of drug is greatly reduced before it reaches systemic circulation.
Define bioavailability.
fraction of an administered dose of unchanged drug that reaches systemic circulation and is available for clinical effect
What are the advantages and disadvantages of administering a drug via the oral route?
Pros = socially acceptable Cons = first pass metabolism effect reduces amount of drug available in the systemic circulation; risk of drug causing irritation and ulceration (e.g. NSAIDs)
Name examples of CV drugs.
Anti-platelets - aspirin, clopidogrel, dypyramidole
Anti-coagulants - warfarin, rivaroxaban, dabigatran
Calcium channel blockers - nifidepine, amlodipine
Nitrates - glycerol trinitrate (GTN)
Anti-arrythmics i.e. Beta blockers - atenolol, propranolol
Lipid lowering drugs - simvastatin
Diuretics - bendroflumethiazide, frusemide
ACE inhibitors - ramapril, lisinopril
What is the dental relevance of calcium channel blockers?
The drugs acting on peripheral blood vessels (nifedipine, amlodipine) can cause gingival hyperplasia.
What are the advantages and disadvantages of administering a drug via intravenous? Give an example of a drug administered this way.
rapid immediate onset of drug, avoids first pass metabolism, continuous and closely monitored administration
requires IV access - can be painful and difficult to obtain (drug users), increased infection risk
MIDAZOLAM
What are the advantages and disadvantages of administering a drug via subcutaneous? Give an example of a drug administered this way.
avoids first pass metabolism, constant slow and prolonged absorption by fatty tissue
needle breaks protective barrier against infection
INSULIN, HEPARIN
What are the advantages and disadvantages of administering a drug via intramuscular? Give an example of a drug administered this way.
rapid onset, shorter duration, muscle can absorb liquid better than subcutaneous layer
neurovascular (nerve) damage, bleeding, painful, infection risk, dependent on blood flow - delayed absorption in shock
GLUCAGON, ADRENALINE
What are the advantages and disadvantages of administering a drug via transdermal? Give an example of a drug administered this way.
avoids first pass metabolism, controlled and continuous release
skin is an effective barrier - only small molecule medications will work
ISOSORBIDE MONONITRATE
What are examples of adverse effects of therapeutic steroids (e.g. hydrocortisone, prednisolone)?
hypertension, type II diabetes, osteoporosis, increased infection risk
What is first order kinetics and zero order kinetics in drug clearance? What graphs do these produce? Give two examples of drugs that are eliminated through zero order kinetics.
1st order = drug elimination is by passive diffusion only; produces logarithmic graph
zero order = drug elimination is an active process, produces linear graph
alcohol and paracetemol
Which route of drug administration gives the most predictable bioavailability?
Intravenous.
What factors affect oral absorption of drugs?
lipid solubility and ionisation, drug formulation, GI motility, interactions with other substances, GI tract disease
What chemical processes may be involved in phase 1 of drug metabolism? What is the effect of phase 2 reactions in drug metabolism?
oxidation, reduction, hydrolysis
conjugation
Describe the action of lipid lowering drugs.
HMG coA reductase inhibitors (simvastatin, atorvastatin)
inhibit cholesterol synthesis in the liver - reduce total cholesterol and LDL cholesterol
side effects: possible myositis with some drug interactions - includes antifungals
