2. Why use drugs?
To improve quality or quantity of life
To cure, suppress or prevent disease
3. Before starting treatment !
Decide whether a drug is necessary. If it is:
1. What are you hoping to achieve?
2. Will the drug chosen will bring this about?
3. What other effects the drug might have – could
these be harmful?
4. Does benefit outweigh risk?
5. How should you choose a drug?
Safety & tolerability
Efficacy
Cost-effectiveness
6. Why take a drug history?
Drugs:
can cause disease (early or late)
can conceal disease
can give diagnostic clues
can interfere with diagnostic tests
history can assist treatment choice
7. History of adverse reactions?
“I can’t take antibiotics, they make me ill,
doctor”
Which specific drugs?
When?
Actual adverse reaction, beware “allergy”
Similar drugs since?
8. Reporting of adverse drug reactions
Yellow card system
All suspected reactions to new drugs
Serious reactions to established drugs
Committee on Safety of Medicines (CSM)
Medicines and Healthcare Devices Regulatory
Authority (MHRA)
9.
10.
11. Responsibilities of the physician?
Not to be ignorant of existing knowledge or
important new developments
To adopt new developments of proven value
To prescribe accurately and clearly
To avoid inappropriate prescribing
To tell patients what they need to know
To accept responsibility for one’s actions
12. What should you tell the patient (1)?
About the condition and why we are treating it
The name of the medicine
– It may help to write this down for the patient
The objective of the treatment
Whether and how the patient will judge benefit
How soon benefit can be expected
13. What should we tell the patient (2) ?
How and when to take the medicine
What to do about a missed dose
How long the medicine is likely to be needed
How to recognise ADRs and how to respond to
them
Important interactions with e.g. alcohol and other
medicines
14. The prescription – pitfalls
Doses
Route
– Choose an appropriate route e.g. is
the patient vomiting?
– Care with doses with different routes
e.g. Penicillin 1.2g iv versus 1.2mg
intrathecal
– Do not use the im route if patient is
anticoagulated
15. The prescription – pitfalls
Doses
Vancomycin
–Cl difficile 125mg qds PO
–Staph aureus 1g bd IV
16. The prescription – pitfalls
Doses
Dose reduction
– Elderly, renal failure, hepatic failure
Children
– Dose often calculated by weight
– Paediatric pharmacopoeia available
17. The prescription – pitfalls
Rate
Bolus vs Infusion
– Vancomycin “red man syndrome”
– Frusemide and ototoxicity
Minutes or hours
ml or mg
– GTN 50mg in 50ml (5% dextrose) at 1
to 10 ml per hour
20. Interactions
Two drugs together
– Beta blockers (IV or PO) and verapamil (IV)
– Phenytoin and the OCP
– Ciprofloxacin and theophylline
– Enzyme inducers vs. enzyme inhibitors
Nutrition
– NG feeding and phenytoin
Diseases
– Ampicillin and EBV
21. Special situations
Pregnancy
– Avoid all drugs if possible – but especially
ACEI, gentamicin, carbimazole,
isotretinoin, misoprostol
Breast feeding
– Avoid most drugs – especially
ciprofloxacin, amiodarone
Renal / Hepatic impairment
– Avoidance, or change in dose –
gentamicin, opiates
22. How can we contain cost?
Appropriate prescribing
Generic prescribing
Therapeutic substitution
Timely discontinuation
However, many patients do not receive
treatment from which they would clearly
benefit (e.g. in hyperlipidaemia and heart
failure)
23. Compliance
Also: adherence / concordance / cooperation
25-50% of patients take < 90% of
prescribed dose
May be due to poor understanding, so
cannot comply
Can occur in the face of good
understanding
24. Main reasons for poor compliance
Poor doctor-patient relationship
Lack of motivation
Forgetfulness
Deliberate intention
Lack of information
Frequency & complexity of drug
regimen (and total number of drugs)
Adverse drug reactions
25. How can we improve compliance?
Form a ‘partnership’ with the patient
Provide oral and written information
Rationalise drug therapy
Plan treatment around the patient’s life
Use ‘patient-friendly’ packaging
Use combined fixed-dose & SR formulations
See the patient regularly
Use dosette box if appropriate
26.
27.
28.
29. Summary
Prescribing is an important responsibility
Potential to do harm as well as good
Good prescribing is fundamental to
being a good doctor
30. “Poisons in small doses are the best
medicines; and useful medicines in
too large doses are poisonous”
William Withering 1789
32. Question 1
An asthmatic presents with a severe exacerbation of
asthma. She has had a dose of steroid, high flow oxygen
and has had a few nebules of Salbutamol and Atrovent.
However, her peak flow is still very low and she remains
tachypnoeic. You are the admitting doctor and after
review by your senior, you are asked to prescribe
intravenous Aminophylline.
A) what important feature in the history do you have
to elicit before this?
B) her weight is 60kg – BNF dose is 5mg/kg loading
given over 20 minutes and 500 microg/kg/hour
maintenance dose in saline or 5% dextrose
Prescribe this on the infusion chart. Write out a
prescription for the nurses to begin this emergency drug.
33. Answer
a) Check not on oral Theophylline. If so do not give a loading dose
and check plasma theophylline levels.
b) Loading 300mg bolus over at least 20 minutes. Written on yellow
infusion chart as:
Date: 21/10/5 Line: IV Type of fluid: 5% dextrose or 0.9% Saline
Additives: Aminophylline 300mg Volume: 100 ml Rate: over 20 mins.
SIGN!!
Maintenance = 30mg/hour. Written on yellow infusion chart as:
Date: 21/10/5 Line: IV Type of fluid: 5% dextrose or 0.9% saline
Additives: Aminophylline 500mg Volume: 500ml Rate: 30ml/hour
SIGN!!
or 500mg in 250 ml dextrose/saline at a rate of 15ml/hour.
34. ADDENBROOKE'S NHS TRUST
PARENTERAL INFUSION PRESCRIPTION AND RECORD OF ADMINISTRATION
SURNAME
Bloggs
Hospital No 12345
FIRST NAMESFred
KV
CONSULTANT
PRESCRIPTION
DATE
Date of Birth 9.6.54
WARD
C7
ADMINISTRATION RECORD
LINE
TYPE OF FLUID/BLOOD
21.10.2005
IV
Sodium Chloride 0.9%
21.10.2005
IV
Sodium Chloride 0.9%
OTHER
INSTRUCTIONS/DRUGS
DR's
SIGNATURE
BATCH No
DATE & TIME
STARTED
NURSES
INITS
DATE & TIME
DISCONT
Aminophylline 300mg 100ml over 20mins
Loading dose
A Doctor
12345
4.1.05 6am
A Nurse
4.1.05 2pm
Aminophylline 500mg 500ml 30ml/hour
Maintenance dose
A Doctor
31425
4.1.05 2pm
A Nurse
4.1.05 10pm
ADDITIVES
Volume
RATE
35. Question 2
A young man has fallen down and sustained a laceration to
his head. He presents to A&E and has a wound that will
require suturing under local anaesthetic. The Sister hands
you a box of vials of Lidocaine 2%. The patient weighs
70kg. Work out the maximum volume of lidocaine 2% you
can use as a local anaesthetic in this patient. – BNF
recommends a maximum dose of 200mg in any patient
What is the maximum dose in mls?
Write out a prescription for this on the appropriate chart
36. Answer
2% lidocaine = 2g in 100 ml
= 2000mg in 100ml
= 20 mg in 1 ml
Max dose is 200mg (in solutions with Adrenaline – max
dose is 500mg) hence maximum volume is 10ml.
Write out on once only prescription chart as:
Date: 21/10/2005 Drug: Lidocaine 2% Dose: 200mg
Route: S/C Time: as and when given
and SIGN!!
37. Answer – Once Only side of
Prescription Card
CHECK FOR ALLERGY STATUS ON PAGE 1
Once Only Prescriptions
Pharm.
Date
Drug (approved name)
21.10.05 Lidocaine
Dose
Route/
other directions
200mg S/C
Time to
be given
Given by
Initials
Time
Signature
1350 a.Doctor
AD
DRUGS NOT ADMINISTERED
Date
Time
Drug
Initials
Reason
Subsequently Given/
Codes
1350
38. Question 3
An elderly man with known epilepsy presents in status
epilepticus. He has already had rectal and intravenous
Diazepam but these have failed to settle his convulsions.
After review by the on call SpR, a decision is made to
write him up for intravenous Phenytoin – loading then
maintenance dose. The BNF states: For IV infusion (use
saline 0.9%) in status epilepticus 15mg/kg at a rate not
exceeding 50mg/minute as a loading dose; maintenance
doses of about 100mg thereafter at intervals of 6 – 8
hours. Work out the correct infusion rates for the
loading and maintenance doses.
Write up an infusion of Phenytoin on the infusion chart.
The patient weighs 80kg. Also write up the regular
maintenance dose on the appropriate drug card.
39. Answer
Loading = 1200mg. (80kg x 15mg/kg). Admin rate not more than
50mg/min hence write as: eg: 1200 mg Phenytoin in 200 ml
saline 0.9% (= 6mg/ml) at a rate of 8ml/min
Date: 21/10/05 Line: IV Type of fluid: Saline 0.9% Additives:
Phenytoin 1200mg Volume: 200ml Rate: 8ml/min SIGN!!
or 1000 mg in 100ml saline (=10mg/ml) at 5ml/min followed by
200mg in 20 ml saline
“
“
at 5ml/min.
= total 1200mg
Maintenance = 100mg tds or qds IV in 100 ml n/saline
Drug: Phenytoin Dose: 100mg
Route: IV Start Date:
21/10/2005 Circle frequencies eg 8,14,22
Additional Instructions: in 100 ml saline SIGN!!!
40. Parenteral Infusion Chart
ADDENBROOKE'S NHS TRUST
PARENTERAL INFUSION PRESCRIPTION AND RECORD OF ADMINISTRATION
SURNAME
Bloggs
Hospital No 12345
FIRST NAMESFred
KV
CONSULTANT
PRESCRIPTION
DATE
21.10.05
21.10.05
WARD
Sex
C7
ADMINISTRATION RECORD
LINE
TYPE OF FLUID/BLOOD
ADDITIVES
Volume
RATE
OTHER
INSTRUCTIONS/DRUGS
DR's
SIGNATURE
IV
Sodium Chloride 0.9%
Phenytoin 1200mg
200ml
8ml/min
Loading dose
A Doctor
OR ALTERNATIVELY
21.10.05
Date of Birth 9.6.54
IV
Sodium Chloride 0.9%
Phenytoin 1000mg
100ml
5ml/min
Loading dose
A Doctor
IV
Sodium Chloride 0.9%
Phenytoin 200mg
20ml
5ml/min
Loading dose
A Doctor
BATCH No
DATE & TIME
STARTED
NURSES
INITS
DATE & TIME
DISCONT
41. Maintenance dosing –
Prescription Chart
Prescription Chart
Surname
Hospital No
Bloggs
Weight
162534
Doctor must also enter this information on FRONT of case folder
Drugs must not be administered unless this box has been complete
First Names
Date of Birth Sex
Fred
3.6.54
Date
Consultant
Ward
Mr K Varty
C7
Regular Prescriptions
Month and date
26th
Tick times or enter other times
DRUG (APPROVED NAME)
6
Phenytoin
Route
100mg IV
Signature
A Doctor
Additional Instructions
8
Start Date
Stop Date
20 10 05
12
14
Pharm
Drug/Substance
21.10.05
None known
M
Height
Dose
DRUG SENSITIVITIES
18
22
AN
42. Question 4
A young girl (weight 50kg) has taken 30 tablets
of Paracetamol 500mg. She is brought into
casualty 8 hours after the overdose. She admits
to taking the overdose with alcohol. Her
paracetamol levels indicate that she is at high
risk of hepatocellular necrosis so the Regional
Poisons Unit advises you to commence an
infusion regime of N-Acetylcysteine (Parvolex).
The BNF states for IV infusion in 5% glucose,
initially 150mg/kg in 200 ml over 15 mins,
followed by 50mg/kg in 500ml over 4 hours then
100mg/kg in 1000ml over 16 hours.
43. Answer
N-Acetyl 7500mg in 200ml 5%glu over 15 mins then
2500mg in 500ml over 4 hours then
5000mg in 1000ml over 16 hours
Write out on yellow infusion card as:
Date: 7/11/3 Line: IV
Type of fluid
Additives
Vol
Rate
5% dextrose
5% dextrose
5% dextrose
N-Acetlycysteine 7500mg
N-Acetylcysteine 2500mg
N-Acetylcysteine 5000mg
200ml
500ml
1 litre
over 15 minutes
over 4 hours
over 16 hours
And SIGN!!
44. Parenteral Infusion Card
ADDENBROOKE'S NHS TRUST
PARENTERAL INFUSION PRESCRIPTION AND RECORD OF ADMINISTRATION
SURNAME
Bloggs
FIRST NAMESFred
CONSULTANT
KV
PRESCRIPTION
DATE
ADMINISTRATION RECORD
OTHER
INSTRUCTIONS/DRUGS
DR's
SIGNATURE
LINE
TYPE OF FLUID/BLOOD
ADDITIVES
Volume
RATE
21.10.05
IV
5% DEXTROSE
N-ACETYLCYSTEINE 7500MG
200ml
over 15 mins
A Doctor
21.10.05
IV
5% DEXTROSE
N-ACETYLCYSTEINE 2500MG
500ml
over 4 hrs
A Doctor
21.10.05
IV
5% DEXTROSE
N-ACETYLCYSTEINE 5000MG
I litre
over 16 hrs
A Doctor
BATCH No
DATE & TIME
STARTED
45. Question 5
An elderly lady presents with confusion, fits
and altered behaviour associated with a low
grade pyrexia. Further investigations go on to
reveal she has herpes encephalitis. The
decision is made to start intravenous
Acyclovir. Work out the dose for this 65kg
woman and write out a prescription on the drug
card.
The BNF suggests 10mg/kg every 8 hours for
simplex encephalitis
46. Answer
650mg Aciclovir in 150 or 200 ml saline/glucose
(ie 5mg/ml or less) tds over 1 hour for total 10
days
On regular drug card:
Drug: Aciclovir
Dose: 650mg
Route: IV
Start Date: 21/10/05
Additional instr: in 200 ml saline 0.9%
Freq: Circle 8,14,22
SIGN!!
47. Maintenance - Prescription Chart
Prescription Chart
Surname
Hospital No
Bloggs
Weight
162534
Doctor must also enter this information on FRONT of case folder
Drugs must not be administered unless this box has been complet
First Names
Date of Birth Sex
Fred
3.6.54
Date
Consultant
Ward
Mr K Varty
C7
Regular Prescriptions
Month and date
26th
Tick times or enter other times
DRUG (APPROVED NAME)
6
Aciclovir
8
Route
650mg IV
Signature
A Doctor
Start Date
Stop Date
21 10 05
12
14
Pharm
Drug/Substance
21.10.05
None known
M
Height
Dose
DRUG SENSITIVITIES
18
AN
48. Further resources
ER-WEB – further information on
prescribing
http://erweb.cbu.cam.ac.uk/?1523
Clinical Pharmacology Unit – Lecture
Slides & further drug calculations
http://www-clinpharm.medschl.cam.ac.uk/
