Prescribing in Special Circumstances Flashcards
(42 cards)
What is treatment burden?
The workload of healthcare for individuals managing long term health conditionss
What is patient capacity in the context of treatment burden?
The degree to which patients can cope with management of their illness
What is pharmacokinetics?
The science of the rate of movement of drugs within biological systems, as affected by the absorption, distribution, metabolism and elimination of medications
What is pharmacodynamics?
The study of the biochemical and physiological processes underlying drug action including mechanism of action, drug/receptor interactions, efficacy and safety profile
What is bioavailability?
The fraction of the administered dose of drug which reaches the systemic circulation
What factors affect bioavailability?
Molecular weight
Absorption
Gastric pH
First pass metabolism
What is the clearance of a drug?
The volume. of plasma which is cleared of the drug per unit time
What is half life?
The time required for serum plasma concentration of a drug to decrease by half
What is the volume of distribution?
The volume in which the amount of drug would need to be uniformly distributed to produce the observed blood concentration
How many half lives does it take for a drug to reach steady state?
4-5 half lives
Loading doses are often used for what kind of drugs?
Drugs with long half lives
Describe the relationship between dose and serum concentration in linear pharmacokinetics?
Doubling the dose. of the drug will result in double the serum concentration of the drug
Why is the serum concentration of a drug not proportional to the dose in non-linear pharmacokinetics?
The dosage increase can saturate binding sites, resulting in non-proportional increases in drug levels
The rate of elimination is constant regardless of the amount of drug present
With age, there is a decreased volume of distribution due to a decrease in muscle mass (and total body water). How might this affect drugs such as lithium and aminoglycosides?
These are water soluble drugs and so their serum concentration will increased with decreased volume of distribution
With age, there is increased body fat. How might this affect fat-soluble drugs such as diazepam and thiopental?
Increased half lives of these drugs
Why can there be an increased propensity to toxicity in elderly patients for drugs which undergo significant first pass metabolism e.g. benzodiazepines?
With age there can be decreased haptic blood flow which decreases first pass metabolism
Why is there a decreased hepatic clearance of drugs with increasing age?
Decrease in oxidative metabolism of drugs through cytochrome p450 with age
What formula is used by pharmacists to calculate creatinine kinase to inform prescribing?
Cockcroft Gault
Give examples of drugs which have increased effects with age?
Alcohol
Opiates
Sedatives
Theophylline
Give examples of drugs which have decreased effects with age?
Isoproterenol
Beta blockers
Give examples of common drug-disease interactions
Increased risk of drug induced confusion in PD
NSAIDs exacerbate heart failure
Urinary retention in BPH with decongestants and anticholinergics
Constipation is worsened by calcium, anticholinergics and calcium channel blockers
Neuroleptics and quinolones lower seizure thresholds
Give examples of common adverse drug interactions
Statins and chlarithromycin
Verpamil and beta blockers
Warfarin and multiple drugs (aspirin)
ACE inhibitors increase hypoglycaemic effect of sulphonylureas
How does renal disease affect pharmacodynamics and pharmacokinetics?
Decreased drug elimination, protein binding and hepatic metabolism
Altered sensitivity to drugs
Increased adverse effects
Give examples of drugs which have decreased elimination in renal disease?
Aminoglycosides Lithium Digoxin Methotrexate Penicillins
