18 - Prescribing

Question 1

What are the 8 steps of prescribing a medicine

Answer 1

1. Make a diagnosis
2. make a therapeutic decision
3. Choose a medicine
4. Chose a dosing regime
5. Write a prescription
6. Counsel the patient
7. Monitor the response
8. Review

Question 2

What is rational prescribing

Answer 2

Selecting the most appropriate therapeutic regimen for a specific patient

Question 3

Make a therapeutic decision

Answer 3

• treatment goals and what the PATIENT wants i.e. are you treating the symptoms or an underlying cause

Question 4

Choose a medicine

Answer 4

Need to consider

• efficacy (consider patient-related factors that would affect this)
• safety (ADRs/contraindications)
• appropriateness (affordability, dosing intervals)

Guided by clinical studies, research and guidelines as to what medicine you use

Question 5

Efficacy

Answer 5

• how effective are the treatment alternatives
• equally effective in all populations
• patient related factors i.e. compliance, meds, disease, age

Question 6

Choosing a dosing regimen

Answer 6

IV
- high conc in blood rapidly
- instant and complete absorption 
Depot
- releases contents slowly 
- compliance good
Skin patches and gels
- lower peak concs and extended duration of effect
- potential for skin ADR
Local delivery 
- site of action targeted
- reduces systemic effects
Oral
- slower rise to peak in conc
- may be less complete absorption
- first pass metabolism

Question 7

Therapeutic index?

Answer 7

Is the dose at a population level that is less likely to cause a problem and most likely to cause benefit

Question 8

What is required on a legal prescription

Answer 8

• drs name and initals
• signature
• address
• MCNZ registration number
• contact number
• patient name
• patient address
• age IF under 13

Needs to be legible

Question 9

Prescriptio 3 parts

Answer 9

Recipe (Rx)
- name of med, strength and formulation 
Sig
- instructions for the patient 
Mitte
- instructions for the pharmacist 
- specifies the quantity to be dispensed

Question 10

Counsel the patient

Answer 10

Make sure they understand…

• reasons for providing the medicine
• the benefits and when they can be expected to occur
• possible adverse effects
• possible interactions
• how to take it

But don’t provide too much info! Need to see patients back after prescribing a new medicine quite quickly

• provide sources of other info
• aids to adherence i.e. blister packs

Question 11

Monitor response

Answer 11

• check for signs of undesirable response
• measure for clinical end point
• monitor using a surrogate biomarker i.e. blood test or bone density
• if there is no easily measured end point or surrgoate - bloods
• monitoring effectiveness of treatment
• decide what you are going to monitor and measure to asses response to treatment and how often

Question 12

Use clinical response…

Answer 12

• cancer treatment
• infection
• nausea

Question 13

biomarker used…

Answer 13

• PSA
• HIV CD4 count
• bone density
• full blood count

Question 14

drug conc…

Answer 14

• digoxin (HF)
• phenytoin (epilepsy)
• Lithium (mood disorders)

i.e. end point is infrequent, serious, not easily measured

Question 15

What are some indications for therapeutic drug monitoring?

Answer 15

• when an event is potentially serious but infrequent
• there is a narrow therapeutic index and small increase in dose can lead to toxicity (phenytoin, digoxin)
• the effects correlate better with conc than dose (when dose and effect don’t have a linear response)
• deciding if a symptom is due to an adverse effect and detecting non-compliance

Question 16

Review the medicine

Answer 16

• assess appropriateness
• effectiveness
• consider the patient view (adherence, understanding, concerns)