Polypharmacy 2

Question 1

5 common classes of medications that cause admissions

Answer 1

• NSAIDs - GI bleed, renal function
• Antiplatelets
• Anticoagulants
• Diuretics - AKI, electrolyte (low Na+), hypotension –> falls risk
• Antihypertensives

Question 2

Where do medication errors commonly occur?

Answer 2

• Primary care
• Care homes
• Secondary care - least common - less patients to look after

Question 3

Where in the journey do prescription errors occur?

Answer 3

• Prescription writing
• Dispensing
• Administration
• Transitions

Question 4

What do clinical pharmacists do?

Answer 4

• Ward round participation
• Monitoring and reporting ADRs - via yellow book (post marketing surveillance)
• Therapeutic drug monitoring
• Prevention and monitoring drug interactions
• Patient counselling re medications
• Clinical research

Question 5

What dose of morphine is suggested to then becomes useless for pain?

Answer 5

120mg per day - after this you begin getting more side effects and battle tolerance issues

Question 6

How to prescribe liquid doses?

Answer 6

• Prescribe dosage - not mls
• As the liquids can come in different strengths

Question 7

What is bioavailability?

Answer 7

• How much of the drug actual makes it to the blood stream to be able to then act on receptors
• It passes through GI tract and liver prior to this - will affect bioavailability depending on formulation (eg tablet, IV, subcut)

Question 8

Morphine - oral to SC calculation

Answer 8

• Divide oral dose by 2
• Subcut = double strength of oral

Question 9

Examples of medicines that should be prescribed by brand

Answer 9

• Anti-epileptics - varies between brands, affects bioavailability, if stable prescribe same again
• Insulin

Question 10

What is medicine reconciliation

Answer 10

• Three C’s
• Collection - new medications, what they take and what they are prescribed, include OTC and herbal
• Checking - against reliable sources (at least 2)
• Communication

Question 11

Sources we can use for medicines reconciliation

Answer 11

• Patient or carer
• Patients own medications (PODs) - supply on d/c
• Patients reminder charts - confirm with pt that they are new
• GP repeat prescriptions
• GP surgery/summary care record
• SystemOne - electronic patient record and recent outpatient letters
• Discharge letters or old drug charts if recently discharged after hospital admission

Question 12

Targets of drugs - where can they act

Answer 12

• Mostly cellular (but not all eg antacid)
• Mostly proteins (either on cell surface or inside cells)
• Mostly receptors (agonists and antagonists)
• But can be ion channels, enzymes and transport proteins
• These are already there biologically, we then use drugs that act on them alongside natural substrate

Question 13

What is pharmacodynamics?

Answer 13

What the drug does to the body - biochemical, physiological and therapeutic effects of drug

Question 14

What is pharmacokinetics?

Answer 14

What the body does to the drug
* ADME
* Absorption - absorbed when reach blood, IV does not require (all others do)
* Distribution - movement of drug around body
* Metabolism - destruction of drug by chemical alteration (usually via liver)
* Excretion - removal of drug from body (eg kidneys or bile)

Elimination = metabolism + excretion

Question 15

How can drug interactions work?

Answer 15

• Pharmacodynamic - Drug A alters action of Drug B - concentation of drug B in tissue fluid is unaltered but effect is altered
• Pharmacokinetic - drug A alters ADME of drug B - concentration of drug B that reaches site of action is altered

Question 16

How do pharmacodynamics interactions work?

Answer 16

• One drug is affected by presence of another
• Compete for same drug target or act on same physiological system (eg lots of antihypertensives different classes = same system)
• Synergistic/additive (same effect/side effect) or antagonistic (oppose eachother)

Question 17

Examples of synergistic effects

Answer 17

• Alcohol + diazepam - enhance GABA neurotransmission - different receptors
• Beta blocker and verapamil - work on same system, different receptors
• Potassium supplement + spironolactone - K+ sparing

Question 18

Antagonistic interactions examples

Answer 18

• Antihypertensives and sympathomimetic decongestants (constricts blood vessels to reduce oedema and help drain nose)
• Anticoagulant and vitamin K
• Gliclazide and glucocorticoids (hypoglycaemia - stimulates pancreas to produce insulin, vs hyperglycaemia)

Question 19

How do pharmacokinetic interactions work?

Answer 19

• Absorption - chelation/complexes (drug binds to drug or food = insoluble complexes not absorbed = therapeutic failure), changes of GI pH (acidic drugs absorb well in acid and same for alkaline), effects on GI motility, food effects (slower absorption if taken with meal and changes pH)
• Distribution - protein bound drugs displacing eachother (on albumin) = increased free drug levels in blood, mostly affects narrow TI drugs eg Warfarin, digoxin, phenytoin
• Metabolism - CYP450 inducers and inhibitors

Question 20

What affects levels of albumin?

Answer 20

• Liver failure - reduced production
• Amino acids poor intake in diet - no ingredients to make albumin

Question 21

CYP450 inhibitors

Answer 21

• Allopurinol (inhibitor) and Azathioprine
• Fluconazole and Warfarin
• Grapefruit juice and Ciclosporin

= increased blood conc of drug

Question 22

CYP450 inducers

Answer 22

• Rifampicin (inducer) and phenytoin
• Carbamazepine and oral contraceptive
• Tobacco and theophylline

= reduced blood conc of drug

Question 23

Drug and food interactions

Answer 23

• Food and absorption of abx
• Calcium in milk –> chelation
• Grapefruit juice being inhibitor
• Cranberry juice increasing effect of warfarin
• Tyramine (sympathomimetic) rich foods eg cheese, beer and wine metabolised by MAO - interact with MAOIs
• Vitamin K rich foods (greens) reducing effect of warfarin
• High protein foods and L-dopa (uses amino acid transporter to cross BBB - high protein meal will compete with L-dopa)

Question 24

Resources to use for checking drug interactions

Answer 24

• BNF interaction checker
• Stockleys drug interactions
• HIV drug interaction checker

Question 25

Criteria for therapeutic drug monitoring

Answer 25

* Poor correlation between dose and effect * Narrow concentration interval between toxic and therapeutic effects * Good correlation between plasma concentation and effects

Question 26

When to take blood samples for TDM?

Answer 26

* 4-5 half lives - when drug reached steady state

Question 27

What is polypharmacy?

Answer 27

* Often 6 or more * Often older patients - more chronic conditions * Not all drugs are positive for patients