Lecture 18: Clinical Pharmacology and Prescribing Flashcards
Importance of Prescribing
something you will do daily
must do safety and effectively
Rational prescribing
Selection of the most appropriate therapeutic regimen for a specific patient
4x Steps prior to writing a prescription
- Make a diagnosis
- Make a therapeutic decision
- Choose a medicine
- Choose a dose regimen
- Making a diagnosis: Examples of patients who come in with symptoms and not diagnoses
- please give me pain relief for a sever headache
- i have a cough that wont go away
- I am constipated. can you prescribe something
* * May think it is something, but also need to be weary that it is something you should be worried about
* * You would use a different treatment if you knew the underlying cuase
- Make a therapeutic decision
Treatment Goals:
1. Identify key management issues with patient (diagnosis, symptom control, disease modification (long-term consequence)
2. Are current symptoms modifiable by symptomatic treatment or disease modifying treatment
- are you going to treat the underlying cause of the disease or the symptoms? e.g Lose ovaries a). hormone replacement therapy with oestrogen. b). antidepressants/anti-epilepsy treatment
- e.g. to long w/o periods - may avoid period symptoms, but can be at risk of endometrial thickening and hence endometrial cancer
Overall: Dialogue with patient and treating the important factors
- Choosing a medicine
a. Efficacy
b. Safety
c. Appropriateness
Note: can choose less effective mechanism due to safety profile or appropriateness
e.g. Oestrogen HRT, even though most effective treatment to relieve symptoms, there is an increased risk of breast cancer, heart attacks and strokes in older woman, therefore people wont take as aren’t happy with the safety profile (esp. important for someone with family history, diabetic, hypertension and are already at risk)
Efficacy of a medicine
How effective are the treatment alternatives?
- what is the evidence to support these treatment alternatives (get advice from boss, reading journals, meetings, public guidelines) (annoying “well informed” patients)
Patient related factors which affect efficacy
age
disease state (e.g. worsened renal function, may handle medication differently)
pregnancy
genetics
other medications (e.g. hot flush medications interfere with breast cancer treatment)
other substances
compliance (wont work if you dont take the medicine)
Safety of medicine
- what are the contradictions for using these drugs in general and specifically in the patient?
-allergies
-concomitant disease including major organ failure - What are common and potentially serious adverse effects that can occur with this drug
- will these side effects affect my choice for this patient - What drug interactions need to be considered?
- drug-drug, drug-food, drug-disease - Is the patient pregnant or lactating
Overall: weigh up the risks and benefits to the treatment
Examples of contradictions for drugs and drug interactions
Dont give osteoporosis medication (which is renally cleared) to a patient with significantly reduced GFR
2x antihypertensive medications causing hypotension
Appropriateness of a medication
Can the patient afford it
Are there any considerations that need to be made for compliance
- more than once a day
- empty stomach
- needs blood test and dose adjustments
e.g. thinking of getting pregnant, patients needs to be aware of teratogenic effects of Topiramate
e.g. wont take meds if makes them feel drowsy (cant drive car etc.)
- Choose a dosing regimen
available in multiple forms
Start at high dose an have lots of side effects vs. start at low dose and work way up to effective dose
e.g. topiramate + gabapentin: pain medication for menopause, but if start at correct treatment dose, people often become too tired and nauseous to continue
there are methods of choosing the dose
5x Routes of delivery (considered when choosing a dosing regimen)
- IV injection
- Skin patches and gels
- Oral tablets
- Depot preparations
- Local delivery
IV injections
high concentrations in blood rapidly
instant and complete absorption
potentially more dangerous
- avoids problems wiht patient compliance
e.g. osteoporosis medication: more effective partially due to levels in the system and partially due to compliance
Skin patches and gels
Lower peak concentration and extended duration of effect
Can bypass first pass metabolism (e.g. in liver)
skin reaction is potential adverse effect