Using the BNF

1. Using the BNF CWFS F1 Programme Safe Prescribing Module

2. 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 • http://www.bnf.org/bnf/bnf/current/

3. 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)

4. 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

5. 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 avoidor use only with caution and intensive monitoring’

6. 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.

7. 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

8. 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

9. 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

10. 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 < 10ml/minute > 700

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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

17. 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

18. Try the quiz to familiarise yourself with your BNF