Contraindications Flashcards
H2 antagonists
Renal failure - because they are excreted by the kidneys
Symptoms of gastric cancer might be disguised by
H2 antagonists and PPIs
Loperamide
Acute UC and C. difficile - inhibition of peristalsis may increase risk of megacolon & perforation - therefore wait until aetiology is known before prescribing to someone in hospital
Laxatives
Suspected intestinal obstruction - could induce perforation
Aminosalicylates
Aspirin hypersensitivity - aspirin is an aminosalicylate
Metoclopramide and Domperidone
GI obstruction or perforation as these drugs promote gastric emptying
Extrapyramidal side effects of anti-emetics (D2 antagonists) are more common in
Children & young adults - AVOID
Loop diuretics
Severe hypovolaemia or dehydration Severe hypokalaemia Severe hyponatraemia Gout - inhibit uric acid excretion Renal failure - nephrotoxic Pregnancy
Thiazide diuretics
Hypokalaemia
Hyponatraemia
Gout - reduce uric acid excretion
Addison’s disease
Potassium-sparing diuretics
Hyperkalaemia
Hypovolaemia
Severe renal impairment
B-blockers
Asthma - can precipitate bronchospasm
Second- or third-degree heart block
Pregnancy
Verapamil and Diltiazem
Poor LV function - worsen heart failure
AV nodal conduction delay - may provoke complete heart block
Pregnancy
Amlodipine and Nifedipine
Unstable angina - vasodilation causes reflex increase in contractility and HR, and therefore increases O2 demand
Severe aortic stenosis
Pregnancy
ACE inhibitors
Renal artery stenosis
AKI
Pregnancy + Breastfeeding
ARBs
Renal artery stenosis
AKI
Pregnancy + Breastfeeding
Nitrates
Severe aortic stenosis - CV collapse because heart unable to increase cardiac output sufficiently through the narrowed valve to maintain pressure in the now dilated vasculature
Hypotension
Digoxin
Second or third degree heart block - worsens conduction abnormalities
Ventricular arrhythmias
Renal failure (reduced dose)
Low Na, Mg, Ca - increased risk of digoxin toxicity
Amiodarone
Heart block
Severe hypotension
Active thyroid disease
Aspirin
<16yrs old - risk of Reye's syndrome Aspirin or NSAID hypersensitivity Peptic ulceration (prescribe with PPI) Gout - may trigger acute attack Pregnancy (third trimester) - premature closure of ductus arteriosus
Clopidogrel
Active bleeding
7 days before surgery or invasive procedures
Heparins
Those at risk of bleeding
Invasive procedures
Renal impairment (may accumulate) - use UFH
Warfarin
Immediate risk of haemorrhage (e.g. surgery)
Liver disease (less metabolism so risk of over-anticoagulation)
Pregnancy (foetus development and maternal bleeding)
Rivaroxaban
Active bleeding or at risk Malignant neoplasms Oesophageal varices Recent eye or brain surgery/haemorrhage Pregnancy + breastfeeding
Statins
Hepatic impairment
Renal impairment (excretion by kidneys)
Pregnant - cholesterol needed for development
Breastfeeding
B2 agonists
CV disease - tachycardia may provoke angina or arrhythmias
Why must long-acting B2 agonists be used in combination with an inhaled corticosteroid
Without this they are associated with asthma deaths
Anti-cholinergics
Angle closure glaucoma - rise in IOP
Arrhythmias
Corticosteroids
Infection
Children - can suppress growth
Oxygen
Type 2 respiratory failure (e.g. severe COPD) - they develop responses to persistent hypoxaemia + hypercapnoea, so exposure to high O2 concentrations can disturb this adaptive state and cause a rise in CO2 blood concentration - this leads to respiratory acidosis, depressed consciousness + tissue hypoxia
Amitriptyline
People at risk of AEs - elderly with CV disease or epilepsy
SSRIs
People at risk of AEs - epilepsy, peptic ulcer, hepatic impairment
Young people - increased risk of self-harm + suicidal thoughts so prescribed by specialists only
Benzodiazepines
Respiratory impairment
Neuromuscular disease
Liver failure
Elderly (reduced dose)
Dopaminergic drugs
Elderly & psychiatric disease (caution) - risk of confusion + hallucinations
CV disease - risk of hypotension
Anti-convulsants
Hepatic impairment (reduced dose) Pregnancy - especially sodium valproate
Penicillins
Penicillin allergy
Renal impairment (dose reduction)
C. difficile risk (amoxicillin)
Flucloxacillin-related hepatotoxicity
Cephalosporins + Carbapenems
Penicillin allergy (or carbapenem or cephalosporin)
C. difficile risk
Epilepsy - carbapenems
Renal impaitment (reduced dose)
Trimethoprim
Pregnancy (first-trimester)
Folate deficiency
Renal impairment (dose reduction)
Neonates + elderly + HIV - more susceptible to AEs
Nitrofurantoin
Pregnancy (towards term)
Babies <3months
Renal impaitment
Not suitable for chronic use due to AEs
Tetracyclines
Pregnancy + breastfeeding
Renal impairment
Aminoglycosides (Gentamicin)
Myasthenia gravis - can impair NM transmission
Neonates + elderly
Renal impairment
Macrolides
Macrolide sensitivity (different to penicillin) Severe renal or hepatic impairment (elimination)
Ciprofloxacin
Seizure risk
Patients still growing
At risk of QT prolongation (e.g. electrolyte disturbance, CV disease)
Metronidazole
Liver disease (reduced dose) Alcohol - inhibits acetaldehyde dehydrogenase, which is responsible for clearing the intermediate alcohol metabolite acetaldehyde from the body
Vancomycin
Needs to be closely monitored in all patients, but reduced dose to avoid toxicity in:
- Renal impairment
- Elderly
NSAIDs
Severe renal impairment -Heart failure -Liver failure -NSAID hypersensitivity If unavoidable, use low dose for: -Prior peptic ulcer -GI bleeding -CV disease
Strong opioids
Respiratory failure Biliary colic - worsens pain due to spasm Reduced dose: - Elderly - Renal or hepatic impairment
Weak opioids
Severe respiratory failure
Reduced dose in elderly, renal or hepatic impairment
Seizures - tramadol lowers threshold
Paracetamol
Chronic alcohol use - increased NAPQI production
Malnutrition or low weight
Severe hepatic impairment
Allopurinol
Do not start during acute attacks of gout
Hypersensitivity to allopurinol
Liver or renal impairment
