Prescribing notes
When thinking about prescribing it can be difficult to know which side effects and contraindications are important to remember. I have therefore compiled a list of common things to look out for when prescribing (which is by no means exhaustive/complete).
Common or noteworthy drug side effects and contraindications:
Tramadol increases seizure risk in patients with epilepsy, and patients on SSRIs, MOAIs and Tricylic antidepressants. They also increase the risk of Seretonin syndrome with SSRIs.
Do not give B blockers and calcium channel blockers mainly targeting the heart (verapamil, diltiazem) together as this can cause bradycardia and arrhythmias.
Avoid B blockers in asthmatics. NSAIDS may also cause bronchospasm and should be avoided if an asthmatic patient has not used NSAIDs before or is symptomatic.
NSAIDs also cause irritation to the stomach lining and should be avoided/given cautiously in patients with a history of GI bleeding, peptic/duodenal ulcers and dyspepsia
Avoid giving ACE inhibitors and NSAIDs with acute kidney injury (acute renal failure).
ACE inhibitors can cause profound hypotension in patients also on loop diuretics, but withholding diuretics can also lead to rebound pulmonary oedema in patients in heart failure. Seek advice in patients with high dose diuretics and start ACE inhibitors slowly in stable patients with small doses of loop diuretics.
Carbamazepine and Carbimazole can cause agranulocytosis - warn patients to seek medical help if they feel unwell or have a sore throat.
Steroids have multiple side effects if taken long term including increased risk of osteoporosis, increased risk of diabetes, thined skin, increased risk of infections, increased risk of stomach ulcers, oedema and heart failure. Patients on long term steroids usually also take a bisphosphonate and calcium and vitamin D supplements to avoid bone problems.
Patient on long term steroids should have their steroids doubled in acute illness, and switched to IV steroids if they are unable to take them orally. Sudden withdrawal of steroids can lead to an addisonian crisis.
Bisphosphonates need to taken with a full glass of water and the patient should stay upright for at least 30 minutes after taking them as it causes gastric irritation. Omeprazole is also commonly prescribed with bisphosphonates to protect the stomach lining.
Most diuretics can cause hyponatraemia. loop diuretics (furusemide) and thiazide diuretics (indapamide, bendroflumethiazide) may cause hypokalaemia, whilst ACE inhibitors and potassium sparing diuretics may cause hyperkalaemia.
Statins cause myalgia commonly and can cause deranged liver function tests. Statins are usually continued unless the transaminases rises by more than 3 times the upper range of normal.
Common drugs causing toxicity:
Drugs before surgery:
Check guidelines in individual hospitals. However as a general guide, continue most medications except:
References:
Brown W, Loudon K, Fisher J, Marsland L, Pass the PSA, Edinburgh, churchill livingstone elsevier, 2014
http://www.fpnotebook.com/Surgery/Pharm/PrprtvGdlnsFrMdctnsPrTSrgry.htm
http://www.uhs.nhs.uk/Media/suhtideal/Doctors/SaferPrescribingWorkbook/Section4Appendix2-Peri-operativedrugs.pdf
Common or noteworthy drug side effects and contraindications:
Tramadol increases seizure risk in patients with epilepsy, and patients on SSRIs, MOAIs and Tricylic antidepressants. They also increase the risk of Seretonin syndrome with SSRIs.
Do not give B blockers and calcium channel blockers mainly targeting the heart (verapamil, diltiazem) together as this can cause bradycardia and arrhythmias.
Avoid B blockers in asthmatics. NSAIDS may also cause bronchospasm and should be avoided if an asthmatic patient has not used NSAIDs before or is symptomatic.
NSAIDs also cause irritation to the stomach lining and should be avoided/given cautiously in patients with a history of GI bleeding, peptic/duodenal ulcers and dyspepsia
Avoid giving ACE inhibitors and NSAIDs with acute kidney injury (acute renal failure).
ACE inhibitors can cause profound hypotension in patients also on loop diuretics, but withholding diuretics can also lead to rebound pulmonary oedema in patients in heart failure. Seek advice in patients with high dose diuretics and start ACE inhibitors slowly in stable patients with small doses of loop diuretics.
Carbamazepine and Carbimazole can cause agranulocytosis - warn patients to seek medical help if they feel unwell or have a sore throat.
Steroids have multiple side effects if taken long term including increased risk of osteoporosis, increased risk of diabetes, thined skin, increased risk of infections, increased risk of stomach ulcers, oedema and heart failure. Patients on long term steroids usually also take a bisphosphonate and calcium and vitamin D supplements to avoid bone problems.
Patient on long term steroids should have their steroids doubled in acute illness, and switched to IV steroids if they are unable to take them orally. Sudden withdrawal of steroids can lead to an addisonian crisis.
Bisphosphonates need to taken with a full glass of water and the patient should stay upright for at least 30 minutes after taking them as it causes gastric irritation. Omeprazole is also commonly prescribed with bisphosphonates to protect the stomach lining.
Most diuretics can cause hyponatraemia. loop diuretics (furusemide) and thiazide diuretics (indapamide, bendroflumethiazide) may cause hypokalaemia, whilst ACE inhibitors and potassium sparing diuretics may cause hyperkalaemia.
Statins cause myalgia commonly and can cause deranged liver function tests. Statins are usually continued unless the transaminases rises by more than 3 times the upper range of normal.
Common drugs causing toxicity:
- Digoxin - confusion, nausea, visual haos, arrthymias
- Lithium - Early to intermediate: Tremor, tiredness, late: arrhtymias, seizures, coma, renal failure, diabetes insipidus
- Phenytoin - Gum hypertrophy, ataxia, nystagmus, peripheral neuropathy, teratogenicity.
- Gentamicin - ototoxicity, nephrotoxicity
- Vancomycin - ototoxicity, nephrotoxicity
Drugs before surgery:
Check guidelines in individual hospitals. However as a general guide, continue most medications except:
- Stop combined oral contraceptives and hormone replacement therapy 4 weeks before surgery.
- Stop warfarin and antiplatelets and switch to LMWH if appropriate unless patient is at high risk eg. has stents etc. Check with the anaesthetist/surgical team in this case.
- Stop ACE inhibitors, potassium sparing diuretics on the day of the procedure as this reduces the risk of post op hypotension.
- Consider doubling long term steroids.
- Stop oral hypoglycaemics - metformin causes lactic acidosis.
- Long acting insulin is usually continued but at a reduced dose, but short acting insulin is stopped whilst the patient is nil by mouth.
- Also consider the need for venous thromboembolism prophylaxis, fluids, analgesics and antiemetics in the perioperative period.
References:
Brown W, Loudon K, Fisher J, Marsland L, Pass the PSA, Edinburgh, churchill livingstone elsevier, 2014
http://www.fpnotebook.com/Surgery/Pharm/PrprtvGdlnsFrMdctnsPrTSrgry.htm
http://www.uhs.nhs.uk/Media/suhtideal/Doctors/SaferPrescribingWorkbook/Section4Appendix2-Peri-operativedrugs.pdf
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