Using the BNF CWFS F1 Programme Safe Prescribing Module

Know Your BNF Guidance on prescribing - Controlled drugs and dependence - Prescribing in palliative care/elderly/children Emergency treatment of poisoning General drug monographs Section 1 to 15 Appendix 1 to 9 Yellow Cards for ADR reporting Advanced Life Support Prescribing in children age/weight/body surface area table

BNF Appendices 1. Interactions 2. Liver disease 3. Renal impairment 4. Pregnancy 5. Breast feeding 6. Intravenous additives (7. Borderline substances 8. Wound management products and elastic hosiery ) 9. Cautionary and advisory labels for dispensed medicines )

Appendix 1 : Interactions Pharmacodynamic Similar or antagonistic pharmacological effects or side effects e.g. opiates Pharmacokinetic When one drug alters the absorption, distribution, metabolism or excretion of another drug e.g. NSAIDs and methotrexate

Appendix 1: Interactions Look for drugs in classes (e.g. Cardiac glycosides not digoxin) Name of interacting drug in blue Black dot interactions indicating ‘Potentially hazardous so avoid or use only with caution and intensive monitoring’

Appendix 2: Liver Disease Dose adjustment in liver disease is more contentious than renal impairment since liver may retain large amounts of its metabolising capacity despite very deranged LFTS Liver disease may alter response to drugs so prescribing should be kept to a minimum Hepatic metabolism is one of main routes of elimination for many drugs Appendix 2 in BNF has information regarding dose reduction etc.

Liver disease Liver disease must be severe before important changes in drug metabolism occur Impaired drug metabolism –Rifampicin, Fusidic acid Hypoproteinaemia (Hypoalbuminaemia is associated with reduced protein binding and increased toxicity of highly protein bound drugs) – Phenytoin, prednisolone Reduced clotting –Warfarin & phenindione Hepatic encephalopathy –some drugs can further impair cerebral function i.e. sedatives, opioids, some diuretics Fluid overload –Oedema can be exacerbated by NSAIDS, corticosteroids Hepatotoxic drugs

Appendix 3: Renal Impairment The basic principles: Reduced renal function can cause problems with certain drugs: Toxicity increased sensitivity poorly tolerated side effects reduced therapeutic effect Some of these problems can be avoided by reducing the dose or using an alternative drug

Renal impairment Dose reduction depends on how drug is eliminated Drugs with minor or no dose related side effects only require simple dose reduction Toxic drugs require dose reduction based on GFR Reduce dose or increase interval between doses If possible avoid nephrotoxic drugs

Appendix 3: Renal Impairment Recommendations are based on severity of renal impairment expressed as GFR Serum creatinine gives a very rough estimation N.B. Elderly/ Tiny Grades of renal impairment: Grade GFR Serum Creatinine Mild 20 –50ml/minute 150 –300 Moderate 10 –20ml/minute 300 –700 Severe 700

Appendix 3: Renal Impairment Take highest severity for borderline values of GFR If a dose needs to be reduced in mild impairment, then action will need to be taken for moderate/severe impairment Sources of information include: –BNF –Summary of Product Characteristics –Ward Pharmacist –Medicines Information

Appendix 3: Renal Impairment Example: Advice for Meropenem Usual dose = 500mg every 8 hours Mild –Increase dose interval to every 12 hours = 500mg b.d. Moderate –Use half normal dose every 12 hours = 250mg b.d. Severe –Use half normal dose every 24 hours = 250mg o.d.

Appendix 4: Pregnancy Drugs can be harmful at any time during pregnancy Only prescribe if essential Benefit to mother needs to be >> risk to foetus Risks differ depending on Trimester 1st trimester –Congenital malformations 2nd & 3rd trimester –Growth & functional development Perinatal –Adverse effects on labour or neonate BNF Tables are not complete –absence does not imply safety

Appendix 5: Breast Feeding Drugs excreted in maternal milk; consider Toxicity Hypersensitivity May inhibit lactation May inhibit infant’s sucking reflex Benefit of breast feeding > need for drug? Use only essential drugs

Appendix 5: Breast Feeding Table lists: Drugs to be used with caution or which are contraindicated Drugs that can be given to the mother –due to small amounts in milk Drugs that can be given to the mother –since not harmful even though present in significant amounts NB: Information not available on many drugs Absence from the table does not imply safety

Appendix 6: Intravenous additives Details of compatible fluids and suggestions of concentrations Sometimes suggests maximum rates Check carefully as not all drugs are compatible with sodium chloride 0.9% Not exhaustive Doesn’t always imply need for IV infusion Ask Pharmacy

Not relevant to medical hospital practice Appendix 7: Borderline substances Appendix 8: Wound management products and elastic hosiery Appendix 9: Cautionary and advisory labels for dispensed medicines

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