Presentation on theme: "Warfarin, Insulin and Digoxin are the most Dangerous drugs in the elderly. Do we believe that?"— Presentation transcript:
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 properlyAll Drugs are DangerousSome drugs have a low therapeutic ratioSome drugs have a low incidence of horrendous effectsSome drugs are dangerous in acute poisoning but not when used therapeuticallyThe most dangerous drugs have the greatest potential for benefitGOODBADSome 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 stoppingHow 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 byChoosing an appropriate class of drug then an appropriate individual agentIs it effective ?What are the chances of adverse effect ?Are there features in this patient which affect choice eg other drugs, organ failure, agedTailoring the doseConsidering duration of treatmentRISKBENEFIT
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 eliminationWide interindividual variation in kinetics and / or responsePharmacokinetics 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 PregnancyBreast feeding
21 BNF chapters of relevance Adverse reactions to drugsPrescribing in the elderlyPrescribing for childrenEmergency 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 patientsIt would take twice as many before there was any suspicion that the effect was due to the drugIf the effect also occurs naturally then it would take many times more patientsMost 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 ADRsSelf reporting by patients and relatives using Yellow cards available at pharmaciesPrescription event monitoringNew drugs – black triangles and yellow cardsEstablished drugs
29 Who reports to the MHRA?Under-reporting estimated at 94% in hospital practice (Smith et al 1996)MRHA activity good at detecting adverse effectsNot 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 ADRsPrescribe as few drugs as possible and give clear instructionsWhere 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