Principles of Prescribing Flashcards
(41 cards)
Definition of adherence
the extent to which a patient’s behaviour matches agreed recommendations from the prescriber. Based on shared decision making between the prescriber and the patient
Definition of compliance
the extent to which a patient’s behaviour matches the prescriber’s recommendations (OLD TERM – criticised for relegating role of patient to one of a passive recipient of medical advice)
Definition of concordance
a belief that decisions about medicines should be shared by a prescriber and a patient so that they can arrive at a harmonious agreement (a concord) regarding therapeutic decisions that incorporate their respective views. Based on:
o Knowledge … education will empower patients to manage their own health. Information should be tailored, clear, accurate and accessible.
o Partnership … invite patients to talk about their medicines
o Support … review medicines regularly with patients
Scale of non-adherence
- In developed countries adherence to long-term therapies as low as 50%
- In UK less than 50% recieve optimal therapy for their condition
- Patients with asthma least compliant - most likely to say costs outweigh the benefits
- In UK, unused/unwanted medicines total £100-300 million annually
Reasons for non-adherence (WHO five factors)
1) Socioeconomic factors - age, geneder, inability to pain for medicines
2) Health system/healthcare team factors - e.g. poor quality of instructions provided to the patient
3) Therapy-related factors - adverse effects, complexity of regimen
4) Patient-related factors - patient disagreement with the necessity for treatment, low self-esteem, low motivation
5) Condition related factors - e.g. dysphagia in myasthenia gravis
Adherence in age groups
- Adolescents less adherent to meds than <12s
- The classic ‘adult’ cohort tends to be ost adherent
- To improve adherence, children <12 should be given the choice of drug formulation
- To improve adherence liquid dosage forms should be first choice preparations for people over 80 years of age
Interventions to improve shared decision making
- Improve communication - aids to improve communication, patient information leaflets (PILs), brail, Yellowcard app (reporting adverse effects) etc
- Increase patient involvement
- Understand the patient’s perspective
- Provide information
Assessing adherence
No agreed gold standard for measuring adherence. Number of approaches adopted:
- Subjective strategies - patient self-reporting
- Objective strategies - measurement of a biomarker or metabolite in blood or urine, e.g. lithium
Interventions to increase adherence
- Simplification of the medication regimen
- Counselling
- Reminders
- Close follow-up
- Supervised self-monitoring - e.g. blood glucose readings, HBPM
- Rewards for success
- Family therapy
- Couple-focused therapy
- Psychological therapy
- Crisis intervention
- Manual telephone follow-up
- Suggest using a Monitored Dosage System (MDS)
Prescription pre-payment certificates (PPCs) and help with healthcare costs
If patient not entitled to free prescriptions (bc they have to pay for >11 prescribed medicines each year or >3 in 3 months), patient can purchase a PPC online
If patient on low income they may be elegible to recieve financial help through NHS low income scheme. HC1 –> HC2 (free prescriptions)/HC3 (help with prescription costs).
New Medicines Service (NMS)
Pharmacy based intervention which provides support for people with long-term health conditions who are newly prescribed a medicine. Patient groups include: Asthma/COPD, T2DM, antiplatelet/anticoag therapy, HTN.
2 intervention dates are set up - 7/14 days and 14/21 days post prescription
Standards for dosing and calculating medications
- SECOND CHECK: good practice to get a second practitioner to check your calculations independantly (especially in case of paediatrics)
- SENSE CHECK: check the calculated dose does not exceed the adult dose or max daily dose, does dose seem reasonable?
- DOCUMENTING WEIGHT REGULARLY: actual body weight (ABW) - stand a pt on a set of scales; Ideal body weight (IBW) - for pts at the extremes of weight as proportions of fat, muscle, bone etc are distorted compared to normal (seek dosing info for these pts); Lean body weight (LBW) - calculated by subtracting body fat weight from ABW
- BODY SURFACE AREA (BSA): some drugs e.g. IV aciclovir rely on this calculation
Paediatric weight calculations
Paediatrics: weight (kg) = (age + 4) x 2
OR
0 to 12 months = (0.5 x age in months) + 4 (kg)
1 to 5 years = (2 x age in years) + 8 (kg)
6 to 12 years = (3 x age in years) + 7 (kg)
These formulas are only to be used in an emergency situ until a measured weight can be obtained
Preparation strengths
Solid dosage forms (e.g. tablets/capsules): expressed as weight per unit e.g. 50mg/tablet
Liquid preparations: expressed as weight per ml e.g. 50mg/ml or 50mg/5ml
Injectable preparations:
- Percentage (% w/v, v/v).
- Amount per ml.
- Total quantity of drug per total volume.
- Ratio (e.g. 1: 1000) = 1g in 1000ml
Conversion factors in dosing
1 kilogram (kg) = 1000 grams (g)
1 g = 1000 milligrams (mg)
1 mg = 1000 micrograms
1 microgram = 1000 nanograms
**micrograms should always be written out in full
Percentage concentrations
%w/w = percentage weight per weight
e.g. hydrocortisone 0.5% w/w contains 0.5 g of hydrocortisone in 100 g of the cream
%w/v = percentage weight per volume
e.g. sodium chloride 0.9% w/v contains 0.9 g of sodium chloride in 100 ml of the infusion.
%v/v = percentage volume per volume
e.g. in a 1% v/v solution there is 1 ml of liquid drug/chemical in 100 ml of the final product.
Conversions from imperial to metric
For weight:
- 1 stone contains 14 pounds (lb).
- 1 lb is equivalent to 450 g.
- 1 stone is equivalent to 6.35 kg.
For height:
- 1 foot contains 12 inches.
- 1 inch is equivalent to 25.4 millimetres (mm).
- 1 foot is equivalent to 304.8 millimetres (mm).
Opioids drug dose equivalents
*Use the lowest dose in the conversion range and then adjust according to response and tolerance
Patients sometimes need to change to alternative opioids because of adverse reactions, intolerance or lack of efficacy.
A table is available in the BNF for converting morphine to fentanyl patches for example… > Prescribing in Palliative Care
Benzodiazepine drug dose equivalents
If a patient is being withdrawn from a benzo, standard practice is to change to an equivalent dose of diazepam then titrate down to zero.
The BNF provides equivalent doses of benzos, all compared to diazepam 5mg > Hypnotics and Anxiolytics
Corticosteroid drug dose equivalents
BNF will base conversion on glucocorticoid activity of drug, disregarding mineralocorticoid activity.
All corticosteroid conversions in the BNF are compared Prednisolone 5mg > Glucocorticoid therapy
Prescribing infusions/medicines for infusion info required
- The name of the active drug
- The total quantity of the active drug to be added to the infusion (if applicable)
- The name and concentration of the diluent (if applicable)
- The total volume of the syringe or infusion bag
- How long the infusion is to be administered over.
- The infusion rate (e.g. ml/hour)
- The infusion rate range (usually in ml/hour) (where applicable)
- The intended dose (e.g. microgram/kg/hour) (where applicable for continuous infusions)
- The route of administration
Prescribing Acetylcysteine in paracetamol overdose
- Calculate dose using actual body weight (ABW), although dose is capped at 110kg body weight
- The diluent - preferably diluted in glucose 5%
- Total dose regimen to be prescribed in 3 parts
- 1st or loading dose given over 1 hour in 200ml of glucose 5%
- 2nd is given over next 4 hours in 500ml of glucose 5%
- 3rd given over next 16 hours, in 1 litre of glucose 5% - Dose of acetylcysteine varies at each step:
- For the first you need 150 mg/kg.
- For the second you need 50 mg/kg.
- For the third you need 100 mg/kg.
- That’s a total dose of 300 mg/kg over 21 hours!
Patient with speech and swallowing problems
- Review meds with advice from a pharmacist. If oral route is used they may be at risk of aspiration or chewing tablets. Drugs can be given enterally via an NG tube if need be
- Decide whether drugs can be easily manipulated, e.g. crushed; discontinued; temporarily withheld; switched to an alternative medicine in same class; switched to alternative route or formulation
- Not always appropriate to crush tablets or open capsules - particularly for MR tablets (drug will be released quickly) or any med that may cause irritation to stomach if coating is broken (i.e. enteric coating, EC). This aso renders drugs off label.
Parenteral routes
- intravenous (IV)
- intramuscular (IM)
- intrathecal (IT)
- subcutaneous (SC)
- topical drops/jel/patch
- intranasal spray
