Safe prescribing

Question 1

Pharmacokinetics with ageing

• Distribution
• Metabolism and elimination

Answer 1

Total body fat increases therefore increasing the volume of distribution for fat soluble drugs.

Total body water however decreases, decreasing the volume of distribution of water soluble drugs.

Serum albumin also decreases and this increases the effects of albumin-bound drugs

Reduced liver volume and enzyme activity means that hepatic metabolism of many drugs decreases

Reduction in the glomerular filtration rate, GFR, is important for drugs that are excreted via the kidneys (digoxin - narrow therapeutic window and renally excreted, needs lower dose and strict control).

Question 2

Sensitivity to drug classes with ageing:

a) Increased
b) Decreased

Answer 2

a) Opiates, BDZs, antipsychotics

b) Beta-blockers, diuretics, beta-agonists

Question 3

STOPP/ START criteria

Answer 3

STOPP (Screening Tool of Older Persons’ Prescriptions) - criteria for potentially inappropriate drugs
(e.g. TCAs in dementia, neuroleptics in Parkinsonism)

START (Screening Tool to Alert to Right Treatment) - criteria for potentially indicated drugs
(e.g. warfarin for chronic AF, ACEI for CCF)

Question 4

Changes for older patients

Answer 4

Digoxin - lower dose
Antipsychotics - lower dose
Heparin - half the dose (renal function)
Warfarin - omit if fall

Question 5

Man with PD on metoclopramide. What should this be changed to?

Answer 5

Change from metoclopramide (D2-blocker) to ondansetron (5HT3-antagonist)

Question 6

Woman with memory issues presents with an MI. She is on diclofenac and oxybutynin.

• What would you start?
• What would you stop?

Answer 6

• Aspirin (and PPI for gastric protection), ACE inhibitor, beta-blocker and statin
• Oxybutynin (could be worsening memory problems), diclofenac (cause gastric ulcer)

Question 7

What changes could be made to dose and frequency of drugs where clearance may be an issue (renal or hepatic)?

Answer 7

Reduce frequency, reduce dose

Question 8

Inappropriate prescribing:

a) examples (CLAN)
b) more common in who?

Answer 8

a) Contraindicated, Length too long, Adverse effects likely, Not prescribing drug that could improve outcome
b) IP is more common in patients receiving polypharmacy, and the elderly

Question 9

Safest opioid to use in the context of renal failure

Answer 9

Safest: Fentanyl, buprenorphine
Use with caution: morphine, diapmorphine, codeine, oxycodone, methadone
Avoid: dihydrocodeine, pethidine

Question 10

Solutions to issues of polypharmacy

Answer 10

EMIS system interactions on SystmOne - 1 star (fine) to 4 stars (do not prescribe)
Getting patients to bring all medications in and any OTC/secondary care meds
Ensure effective communication and concordance with patient
START/STOPP doctrine