geriatric pharmacology Flashcards
absorption in the elderly
rate of absorption may be delayed
lower peak conc
delayed time to peak conc
factors affecting absroption
adminstration what is taken w the drug comorbidity increased GI pH decreased gastric emptying dysphagia
effect of aging on volume of distribiton
1) Reduced lean body mass
- reduced VD for drugs that bind to muscle
2) Reduced body water
- reduced VD for hydrophylic drugs
3) Reduced plasma protein (albumin)
- increased % of unbound or free drug
4) Increased fat store
- increased VD for lipophilic drugs
5) Increased plasma protein
- reduced % of unbound or free drug (active)
drug modifications
liver metabolised in 2 phases
most metabolise in phase 1
- bioavailability may be increases in first act as less drug is extracted by the liver
phase 1
modification (oxidation, reduction, hydrolysis)
- converts drugs into metabolites to facilitate excretion (results in active metabolite)
phase2
adds charged species
medication undergo phase II hepatic metabolic preferred in elder duet o inactive metabolites
- safe for its with liver issues
elimination of drugs
kidney
- if kidney not working, drug accumulation and increase in half life
if drug accumulation occurs increase in toxcity and side effects
causes of kidney reduction function in the elderly and results in
- Decreased kidney size
- Decreased renal blood flow
- Decreased number of functional nephrons (part of the kidney which absorbs)
- Decreased tubular secretion
Result
- Decreased glomerular filtration rate (GFR) – less drugs enter stream of elimination
- Decreased drug clearance: (i.e. gabapentin, H2 blockers, digoxin)
HOWEVER DRUG ABSROPTION IS NORMAL IN ELDERLY
factors which contribute to adverse drug reactions in elderly pts
impaired organ function multiple disease states altered drug concentration decreased homeostasic regulation altered compliaance adverse drug reaction
risk factors for adverse drug events
poly pharmacy
co morbidity
low BMI
drug drug interactions causes
1) Increased or decreased drug’s absorption
2) Additive effects due to similar effects of drugs
3) Antagonizing effects due to opposite effects of drugs
4) Changes in drug metabolism (inhibition or induction)
5) Duplication of drug therapy
what can dementia do
increase sensitivity to drugs with CNS or anticholinergic activity
what are the most common interactions between
cardiovascular and psychotropic drugs
risk of
- confusion cognitive impairment hypotension acute renal failure
best way to prescribe in elderly
1) Start with a low dose and titrate slowly
- wait to see effect
2) Avoid starting 2 agents at the same time
3) Reach therapeutic dose before switching or adding agents
4) Determine therapeutic endpoints and plan for assessment
5) Avoid prescribing to treat side effect of another drug
6) Use 1 medication to treat 2 conditions
7) Consider drug-drug and drug-disease interactions
