1. Warfarin, Insulin and Digoxin are the most Dangerous drugs in the elderly.
Do we believe that?

2. How dangerous a drug is depends on the skill of the prescriber
No Drugs are Dangerous if used properly
All Drugs are Dangerous
Some drugs have a low therapeutic ratio
Some drugs have a low incidence of horrendous effects
Some drugs are dangerous in acute poisoning but not when used therapeutically
The most dangerous drugs have the greatest potential for benefit
GOOD
BAD
Some adverse effects can be predicted if you know the pharmacology (Type A); some are not (Type B)
Some adverse effects occur after a delay or after stopping
How dangerous a drug is depends on the skill of the prescriber

3. The Risk to Benefit Ratio
When prescribing drugs a doctor must assess risk to benefit ratio in the individual patient by
Choosing an appropriate class of drug then an appropriate individual agent
Is it effective ?
What are the chances of adverse effect ?
Are there features in this patient which affect choice eg other drugs, organ failure, aged
Tailoring the dose
Considering duration of treatment
RISK
BENEFIT

4. The Risks when prescribing drugs with a low therapeutic ratio are greatly increased if
Pharmacokinetic process is complicated eg high hepatic extraction, or zero order elimination
Wide interindividual variation in kinetics and / or response
Pharmacokinetics sensitive to drug interaction, disease or ageing

5. Adverse drug reactions   An ADR is any unwanted effect resulting from a drug’s use in treatment.  

6.   Epidemiology 4% of hospital admissions 1 in 1000 deaths in medical wards 10 to 20 % of in-patients 5% of patients in general practice

7. More frequent in elderly:. erratic drug taking. multiple pathology
More frequent in elderly: erratic drug taking multiple pathology altered pharmacokinetics increased sensitivity of CNS and CVS

8. Drugs - anti-coagulants, NSAIDs,corticosteroids, anti-hypertensives, anti-biotics, diuretics and insulin.  

9. Occur in circumstances related to drug’s pharmacology, predisposing factors in the patient and care taken in choosing the drug and the dose.

20. The BNF appendices Drug Interactions Liver disease Renal impairment
Pregnancy
Breast feeding

21. BNF chapters of relevance
Adverse reactions to drugs
Prescribing in the elderly
Prescribing for children
Emergency treatment of poisoning

22. Detecting Adverse Effects
If a new drug causes a bizarre effect in 1 in 6000 patients it would need patients to use the drug for it to occur in 3 patients
It would take twice as many before there was any suspicion that the effect was due to the drug
If the effect also occurs naturally then it would take many times more patients
Most early trials involve about 2000 patients

23. Detecting Adverse Effects
MRHA (Medicine and Healthcare products Regulatory Agency) freephone service for reporting and information about suspected ADRs
Self reporting by patients and relatives using Yellow cards available at pharmacies
Prescription event monitoring
New drugs – black triangles and yellow cards
Established drugs

27. Measuring danger
MHRA activity through Yellow card reporting and prescription monitoring
Huge increase in reports over recent years

29. Who reports to the MHRA?
Under-reporting estimated at 94% in hospital practice (Smith et al 1996)
MRHA activity good at detecting adverse effects
Not very good at assessing the risk ratio

30. Prevention of Adverse Drug reactions
Never use any drug unless there is good indication. If the patient is pregnant do not use the drug unless the need is imperative.
Allergy and idiosyncrasy are important causes of ADRs. Ask if the patient had previous reactions.
Ask if the patient is already taking other drugs including self medication

31. Preventing ADRs cont’d
Age, hepatic and renal disease may impair clearance of drugs so smaller doses may be needed. Genetic factors may also predispose to certain ADRs
Prescribe as few drugs as possible and give clear instructions
Where possible use familiar drugs. With new drugs be particularly alert for ADRs and unexpected event.
If serious ADRs are liable to occur warn the patient

32. Some websites www.yellowcard.gov.uk http://medicines.mhra.gov.uk