Presentation on theme: "Warfarin, Insulin and Digoxin are the most Dangerous drugs in the elderly. Do we believe that?"— Presentation transcript:
Warfarin, Insulin and Digoxin are the most Dangerous drugs in the elderly. Do we believe that?
All Drugs are Dangerous No Drugs are Dangerous if used properly How dangerous a drug is depends on the skill of the prescriber The most dangerous drugs have the greatest potential for benefit Some drugs are dangerous in acute poisoning but not when used therapeutically Some drugs have a low therapeutic ratio Some drugs have a low incidence of horrendous effects 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 BAD GOOD
RISK BENEFIT 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 The Risk to Benefit Ratio
The Risks when prescribing drugs with a low therapeutic ratio are greatly increased if 1.Pharmacokinetic process is complicated eg high hepatic extraction, or zero order elimination 2.Wide interindividual variation in kinetics and / or response 3.Pharmacokinetics sensitive to drug interaction, disease or ageing
Adverse drug reactions An ADR is any unwanted effect resulting from a drugs use in treatment.
Epidemiology 4% of hospital admissions 1 in 1000 deaths in medical wards 10 to 20 % of in-patients 5% of patients in general practice
More frequent in elderly: erratic drug taking multiple pathology altered pharmacokinetics increased sensitivity of CNS and CVS
The BNF appendices Drug Interactions Liver disease Renal impairment Pregnancy Breast feeding
BNF chapters of relevance Adverse reactions to drugs Prescribing in the elderly Prescribing for children Emergency treatment of poisoning
Detecting Adverse Effects If a new drug causes a bizarre effect in 1 in 6000 patients it would need 18000 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
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
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
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
Preventing ADRs contd 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
Some websites www.yellowcard.gov.uk http://medicines.mhra.gov.uk www.dsru.org http://eis.bris.ac.uk/~pmcjcr/Drug%20Safet y.pdfhttp://eis.bris.ac.uk/~pmcjcr/Drug%20Safet y.pdf