Prescribing in the Elderly Flashcards
What is meant by pharmacokinetics and pharmacodynamics?
Kinetics = how drug works on the body Dynamics = how the body works on the drug
What are the 4 parts of Pharmacokinetics?
A - Absorption
D - Distribution
M - Metabolism
E - Excretion
What difference occurs in the elderly when patients are prescribed BOTH atorvastatin and dabigatran (DOAC)?
This combination in the elderly increases the activity of dabigatran(DOAC) by 18%
Give examples of patient groups in which doses/strengths must be altered
Decreased renal function
Overweight/obese
What are the 2 main principles of drug absorption?
Acidic drugs require an acidic environment for absorption
Basic drugs require a basic environment for absorption
Give examples of acidic drugs which require an acidic envrionment for absorption?
Phenytoin
Aspirin
Penicillins
Give examples of basic drugs which require a basic environment for absorption?
Diazepam
Morphine
Elderly patients tend to have a higher gastric pH than younger patients. TRUE/FALSE?
TRUE
therefore their stomach is more basic and basic drugs get absorbed better
What condition may affect the absorption of drugs via a transdermal patch?
Oedema
What is the best way to deliver drugs in patients with dysphagia?
Liquid formulations (syrups etc)
What is the best way to deliver drugs to patients with an NG or PEG feeding tube?
Consult BNF to check if any tablets can be crushed for use in these devices
If patients are confused and refusing tablets, in what ways can these medications be delivered?
Patches
Intravenous infusions
Intramuscular injections?
If patients are null by mouth in preparation for surgery, which of their medications can and cant they omit?
- Antiplatelets should be taken
- Statins can be missed
- BP should be checked and judgement made on the reading (if they become hypertensive this can be sorted in surgery)
How are drugs distributed throughout the body?
- Bound to proteins
- Bound to lipids/dissolved in lipid
- Dissolved in water
What protein molecules are responsible for binding acidic and basic drugs?
ACIDIC = albumin (=> albumin itself is BASIC)
BASIC = Alpha-1 Acid Glycoprotein (=> it is ACIDIC)
Explain the ratio of albumin to alpha-1 acid glycoprotein in the elderly and how this contributes to pharmacodynamics?
Elderly have LOWER albumin than alpha-1 acid glycoprotein
=> they absorb more BASIC drugs
A loss in muscle mass contributes to increased fat in the elderly. How does this affect drugs which are lipid soluble?
Gives lipophilic drugs a bigger volume to distribute themselves across
=> drug has a longer half life
What can decrease the volume of distribution of certain drugs in the elderly?
Less body water in older people
=> less Vd for water soluble drugs (Lithium and Digoxin)
What factors can affect hepatic metabolism in the elderly?
Reduced liver function due to:
- decreased size
- decreased blood flow
- disease
- bio-transforming enzymes are reduced in the elderly
Why is it a problem if elderly patients cannot complete first pass metabolism?
Some drugs require this process to be broken down into their active parts
=> patient wont receive any benefit from drug if their liver cannot break it down
A small concentration of drug in the blood means what in regards to the volume of distribution?
Means the drug is very lipid soluble and dissolved in a large Vd and not much has dissolved in blood
What happens to lipid soluble drugs when patients become cahectic?
- Cahectic patients break down fat stores for energy/metabolism
- the drugs which have been stored in the adipose tissue are then released and drug concentrations increase if these are measured
Generally lower doses achieve same effect in the elderly. TRUE/FALSE?
TRUE
e.g. think alcohol
Why should drugs with a narrow therapeutic index be avoided?
there is not much between their effective concentration and their toxic concentration
=> dangerous for elderly patients with differences in pharmacodynamics
Give examples of drugs with a narrow Therapeutic Index (TI)
Warfarin
Lithium
Digoxin
Gentamicin
Elderly patients are more likely to experience adverse drug reactions than younger patients. TRUE/FALSE?
TRUE
What 4 drugs top the list for the most elderly patients developing adverse drug reactions?
- Warfarin
- Digoxin
- Insulin
- Benzodiazepines
In what situations can we anticipate drug side effects and prescribe preventative measures?
Opioids
- Begin laxative prophylactically
Steroids
- Osteoporosis prevention
- beware of Steroid induced diabetes
Levothyroxine – Calcium interferes with absorption
=> take thyroxine in morning and Ca at night
What drugs should be avoided if possible due to known side effects in the elderly?
NSAIDs - GI bleed, decline in GFR
OPIOIDS/ Benzodiazepines - falls/confusion
ANTIBIOTICS - Resistance, CDiff
What is the BEERS criteria and what are the 3 sections it possesses?
Criteria of medication that shouldn’t always be used in older adults
3 sections:
1) ALWAYS avoided
2) POTENTIALLY inappropriate – depending on comorbidity
3) Used with CAUTION
What would make an older patient at risk of side effects/ ADRs?
- Recent discharge from hospital
- Use of multiple drugs and prescribers
- Impaired cognitive status
- Drugs with a narrow therapeutic index
- Use of OTC meds alongside others
What is the average number of prescription and non-prescription medicines taken by a patient > 65 years of age?
4 prescription drugs
2.5 over-the-counter medicines
What is the average number of prescription drugs given to patients >65 in a nursing home?
7 medicines
What principles should be used to avoid/ fix polypharmacy?
- Review medications and indications regularly
- Discontinue unnecessary medication
- Avoid treating adverse reactions/side effects
- Prescribe a drug that will treat >1 problem (e.g CCB/BB for BP and angina)
- If stable, use combination preparations
What is the STOPP-START tool and how is it used?
STOPP: Screening Tool of Older People’s Potentially Inappropriate Prescriptions
START: Screening Tool to Alert Doctors to Right Treatments
=> List of drugs to STOP in certain pts and list to START if not on already
Give an example of a GI drug which is on the STOPP list for patients with undiagnosed diarrhoea?
Loperamide OR codeine phosphate
prescribing these drugs causes a risk of delayed diagnosis as it temporarily fixes the problem
Give an example of a GI drug which is on the START list?
PPIs should be started for patients >80 years on anti-platelets and SSRIs
Give an example of a cardio drug on the STOPP list?
Statins
Atorvastatin 80mg for no longer than 6 months post-MI
- dose should be titrated down
What factors may influence an elderly patients adherence/compliance to medication?
Can they open the pill container?
Do they understand when and how to take it?
Are they remembering to take their medications?
What was the FAME trial and what did it show?
Trial with patients aged ≥ 65 years on >4 chronic medications who were living independently.
Patients were educated on their tablets
Given regular follow-up (2 monthly)
Medication arranged into customized blister packs
Showed increase in compliance from 60 to ~97%
