Pharmacology Flashcards
Short term effects of anticholinergics?
- confusion
- hallucinations
- tachycardia
- blurred vision
- urinary retention
- constipation
- dizziness
Long term consequence of anticholinergics?
- risk of dementia
Examples of drugs that have an anti-cholinergic effect?
- parkinsons drugs
- antidepressants
- antiemetics
- opiates
Explain anticholinergic burden
- summative effect with multiple prescriptions
Bleeding ulcer stop which drug?
- NSAID
Kidney failure stop which drug
- ACEi
Severe hyponatraemia stop which drug?
- antidepressant
- bendrofluazide
Describe futility
- prescription of a drug with no benefit
Alpha blocker + anti-hypertensive may cause?
- postural hypotension
Define pharmacodynamics
- what the drug does to the body
Define pharmacokinetics?
- what the body does to the drug
- absorption
- distribution
- metabolism
- excretion
How might pharmacokinetics change as we age?
- absorption favours basic drugs due to gastric pH
- less albumin means less acidic drug binding and more basic
- decreased muscle mass, and increased fat increases the distribution of lipophilic drugs
- decrease in body water reduces hydrophilic drug distribution
Explain changes to gastric pH as you age and how that might affect drug absorption
- as we age the gastric contents become more alkaline (pH> 7.35), meaning they absorb basic drugs better
Explain the changes to protein binding as we age?
- albumin decreases so less acidic drugs bind
- more alpha 1 acid glycoprotein so more basic drugs are bound
Explain lipid binding changes as we age
- older people have reduced muscle mass and increased fat
- increased distribution of lipophilic drugs
Explain water volume changes as we age an the affect on drug distribution?
- decrease in body water
- less hydrophilic drugs are transported
What is the volume of distribution?
- theoretical volume which all of a drug is dissolved in plasma
- indicator of lipophicity of drugs
- increased in volume of distribution = very lipophillic
What is the total body water contents?
- 42L
Equation for the volume of distribution?
Dose / [DRUG]plasma
Equation for half life
0.69 x Vd / clearance
Define half life of a drug
- time taken for a drug concentration to fall to half of its maximum concentration
= 0.69 x Vd / clearance
Calculation for clearance
Cl (renal) + Cl(hepatic)
Changes to a drugs half life in the elderly and why?
- half life reduced
- clearance reduced
- liver function decreased and renal metabolism decreased
What is the therapeutic index and how is it calculated?
- range in which a drug is prescribed is safe and effective
= Maximum therapeutic conc / minimum effective conc
