questions Flashcards
(32 cards)
What is metformins mode of action?
- Reduces glucose produced by the liver
- increases sensitivity of muscles cells to insulin produced
- delays transfer of glucose from intestinal tract to blood after meal
Metformin half life?
Three hours
Onset to drug action of metformin?
2.5 hrs
Name a plasma protein and drug which is highly plasma protein bound
Discuss their role in binding drugs and affecting their availability for pharmacodynamic action
Albumin
Warfarin
Drugs bound are pharmacologically inert, don’t reach site of action
Can mean oral dose is greater than needed due to bioavailability being reduced due to plasma protein bonding
Can be displaced by other drugs from their binding sites
What is bioavailability?
Percentage of administered drug that reaches systemic circulation after absorption
What is steady state?
When drug going into the body is equal to going out, achieved after 5 half lives
Which organ produces plasma proteins?
Liver
In liver disease there are changes to plasma proteins meaning less of the drug is protein bound and more of the drug can exert effect- lower dose needed
Example for pharmacokinetic drug interaction
Can occur when drug alters after adme eg magnesium reduces ansorbion of iron so should be separated by time (in bnf)
Example of pharmacodynamic interaction
Competition at receptor sites eg propanalol (antagonist) and salbutamol (agonist)
2 types of ADRs
Augmented- predicted by pharmacology
Bizarre- wholly unpredictable eg anaphylaxis
How to avoid/minimise ADRs
Prescribe familiar drugs Only prescribe if indicated Check for allergies Ref meds reviews to check for polypharmacy Give clear instruction to the pt Check bloods Advise others of potential side effects Previous reactions to medications
What is an ADR
Unwanted or harmful reaction, always unwanted
What to consider when prescribing in the elderly
Decreased metabolism and excretion Polypharmacy Check for renal/liver impairment Only prescribe if good indication Review regularly Check nutrition status
Factors to consider when prescribing in renal impairment
Only px if definite indication
Choose drug with minimal nephrotoxicity
Monitor pt carefully- rev bloods
Factors to consider when prescribing a drug
Route Allergies Co morbidities Age Other medications Patient agreement
What factors influence metabolism?
Genetics
Age- 1st pass maybe reduced in older people
Liver and cardiac disease (reduced blood flow in cardiac, liver disease reduces metabolic potential
What factors can influence ‘time to onset’
Route of administration
Rate at which it is absorbed
How it is distributed by the body
What are pharmacokinetics?
The way the drugs move through the body
Pharmacodynamics?
The effect the drug has on the body
Physiological factors affecting absorption
Blood flow
Total surface area (intestine, large surface area)
Contact time at site
Physio chemical factors affecting absorption
Solubility
Chemical stability
Lipid to water partition coefficient (cells made from phospho-lipid layer- drugs dissolve well in lipids eg anaesthetic, benzodiazepines
Degree of ionisation
What affects distribution
Distribution of body fluids (plasma, interstitial, and intercellular fluid)
Uptake to organs (eg iodine- thyroid gland)
Extent of plasma protein binding
Passage through barriers (eg placenta)
2 phases of metabolism
Phase 1- oxidation (chemical reaction that changes drug properties), reduction, hydrolysis
Phase 2- conjugation
What factors affect metabolism?
Nutrition
Age- enzyme activity declines
Alcohol
Genetics
Disease process, such as heart failure
