Pharmacology Flashcards
What is the definition of anticholinergic burden?
The cumulative effect of medications that have anticholinergic properties
What pharmacokinetic changes occur with aging?
Absorption - slowed gastric emptying, inc gastric pH, dec small bowel surface area
Distribution - body fat increases (longer half life lipophilic), total body water decreases (inc plasma conc of hydrophilic)
Metabolism - hepatic first pass metabolism decreased
Elimination - renal decreased
How do pharmacokinetic changes affect morphine in an older patients?
Absorption - no change
Distribution - morphine is hydrophilic, higher conc
Metabolism - dec first pass metabolism
Elimination - renal decreased
What are the mechanisms of action of donepezil, rivastigmine and galantamine?
Donepezil - reversibly inhibits acetylcholinesterase
Rivastigmine - reversibly (pseudo) inhibits both acetylcholinestase and butylcholinesterase
Galantamine - reversibly inhibits acetylcholinesterase, binds to presynaptic Ach nicotinic receptor and inc AcH release
List 6 evidence based benefits of cholinesterase inhibitors
- Improved cognition (MMSE, ADAS-Cog)
- Improved behaviours (NPI, SIB)
- Improved function
- Improved global clinical state
- No evidence for QOL
What are 2 pharmacokinetic differences between intrajejunal levodopa gel and oral?
Intrajejunal bypasses impact of gastric emptying which can affect rate of absorption of oral = variable blood concentration
IJ more stable concentration, oral has short half life and more rapid wearing off
What is the main motor symptom that IJ Sinemet helps with?
Off symptoms (motor fluctuations)
What antidepressant would you not prescribe in a patient with hx of seizures?
Bupropion - lowers seizure threshold
What 6 categories of interventions to improve medication adherence?
- Clinical pharmacist consultation
- Patient education
- Incentives to promote
- CBT
- Medication regimen management
- Medication taking reminders
What are absolute contraindications to cholinesterase inhibitors?
- Hypersensitivity (drug monograph)
Off drug monograph - High grade cardiac condition block (second or third degree in unpaced, except RBBB)
- Bradycardia <50 bpm
- QT prolongation
What are precautions when using cholinesterase inhibitors?
- Not recommended if cardiac conduction abnormalities
- PUD, NSAID, high dose ASA - monitor
- Bladder outflow obstruction
- COPD/asthma
- May lower seizure threshold
- Rare rhabdo
- Rare NMS
What are 2 drug categories associated with C diff infections?
- PPIs
- Systemic antibiotics
Why should someone on DOAC not take clarithromycin?
Clarithromycin (also ketoconazole and itroconazole) is a CYP3A4 and P-gp inhibitor
Apixaban, rivaroxaban and dabigatran are P-gp substrates
Clarithromycin therefore decreases clearance of DOACs leading to inc levels and bleeding
What is the drug interaction between paroxetine and tramadol?
Paroxetine = CYP2D6 inhibitor
Tramadol = substrate of CYP2D6
This leads to inc tramadol = serotonin reuptake inhibition
In combination with SSRI leads to serotonin syndrome
Compare cholinesterase inhibitors with regards to their distribution
Donepezil - 96% plasma protein bound (esp albumin)
Rivastigmine - 40% plasma protein bound
Galantamine - 18% plasma protein bound
Compare cholinesterase inhibitors with regards to their metabolism
Donepezil - slow extensive liver metabolism by CYP3A4/2D6, glucoronidation. Half life 58-90 hrs.
Rivastigmine - extensive rapid first pass metabolism, doesn’t use P450
Galantamine - metabolized by liver, using CYP3A4/2D6, glucuronidaiton
What medications can cause B12 deficiency?
- PPI
- H2 blockers
- Metformin
- Colchicine
- Phenytoin
What pharmacokinetic reason can cause phenytoin toxicity?
Phenytoin is 90% bound to plasma proteins (albumin) and in unbound form is active
If you have malnutrition = low albumin = inc unbound phenytoin = phenytoin toxicity
What are 4 adverse outcomes of benzodiazepines use in the elderly?
- Memory impairment
- Inc risk falls/fractures
- Inc mortality risk
- Psychomotor retardation
- Inc accidents
- Respiratory issues in COPD