Drug Interactions Flashcards
What are some common drug interactions with ACE inhibitors and ARBs?
K+ increasing drugs- increased risk hyperkalaemia, hypotension and renal impairment
Alcohol- enhanced hypotensive effect
Diuretics- enhanced hypotensive effect
Lithium- reduces lithium excretion= toxicity
What are some common drug interactions with beta-blockers?
ACE inhibitors- enhanced hypotensive effect
Anti-arrhythmic drugs- ventricular arrhythmias
Antidepressants (citalopram, escitalopram and venlafaxine)- risk of ventricular arrhythmia
What are some common drug interactions with CCBs?
Alcohol- increased hypotension risk
Simvastatin- max 20mg dose when used alongisde verapamil, amlodipine and diltiazem
Carbamazepine- may reduce CCB levels
Grapefruit juice- increase in plasma conc. of CCB
What are some drugs that tend to be contraindicated or need dose adjustements in CKD and AKI?
NSAIDs (avoid)
Diabetes medications (adjust)
PPIs (adjust)
Statins (adjust)
ACE inhibitors (adjust)
Why is the use of digoxin alongside quinidine contraindicated?
Can lead to a significant increase in digoxin plasma concentration
Why should sildenafil and isosorbide mononitrate not be used together?
Sildenafil can hugely increase the hypotensive effects of iso.
What are some common drugs that should not be used alongside warfarin/need to be monitored?
-Aspirin and clopidogrel- bleed risk (all anticoagulants and antiplatelets)
-Azathiprine- decreases warfarin effect
-Budesonide- inreases effects of warfarin
-NSAIDs’
-Antidepressants: citalopram, paroxetine
-Antibiotics: doxycycline, amoxicillin, ciprofloxacin, clarithromycin, metronidazole
-Ketoconazole and fluconazole
What are some drug examples of enzyme inducers?
Sulphonylureas
Carbamazepine
Alcohol
Rifampicin
Phenobarbital
Cigarette smoke
Griseofulvin
Phenytoin
St John’s Wort
What are some examples of enzyme inhibitor drugs?
Ciprofloxacin
Isoniazid
Cimetidine
Sulfonamides
Alcohol binge drinking
Metronidazole
Chloramphenicol
Grapefruit juice
Omeprazole
Fluconazole
Ketoconazole
Erythromycin
Sodium valproate
What drugs are contraindicated or cautioned in heart failure?
NSAIDs- CI
Pioglitazone- CI
Beta blockers- CI
Saxogliptan- Cautioned
What drugs are contraindicated and cautioned in asthma?
Beta-blockers: CI
Aspirin- caution
NSAIDs- caution
What drugs are contraindicated and cautioned in epilepsy?
Tramadol- CI
SSRIs- CI
Quinolones- Caution
Burpropion- CI
Antihistamines- Caution
Drugs in Children
-Aspirin- avoid in under 16s
-Codeine- avoid in under 12s due to increased risk of _ side-effects
-Tetracycline- avoid in under 12s
-Bonjela- avoid in under 16s
Respiratory
Antibiotics in Pregnancy
Carrying Mothers Cannot Take Antibiotics
Clarithromycin
Metronidazole
Chloramphenicol
Tetracyclines
Aminoglycosides
What drugs can interact witb SSRIs?
-NSAIDs- increased bleeding risk
-Grapefruit juice- can increase SSRI levels
-St John’s Wort- serotonin syndrome risk
-Tamoxifen- may reduce levels
-Lithium- Increased QT prolongation risk
What are four drugs that can cause vitamin B deficiency?
Metformin
PPI
H2-receptor antagonists
Colchicine
Methotrexate Interactions
Increases toxicity risk:
- Aspirin
-Amoxicillin
-NSAIDs
-Ciprofloxacin
-PPI’s (decreases clearance of methotrexate)
-Flucloxacillin
-Herpes vaccine/Flu vaccine (live)/MMR vaccine (live)- increased generalised infection risk
-Indometacin
-Levetiracetam
-Phenoxymethylpenicillin
-Trimethoprim
.
What are some medications that interact with oral antifungals?
CYP3A4 inducers (carbamazepine, phenobarbital, phenyotin etc)
Anticoagulants/antiplatelets, such as warfarin, clopidogerel and aspirin
Some antibiotics such as ciprofloxacin and erythromycin
Some antipsychotics
Beta-Blocker Contraindications
- Asthma/COPD (cardioselective beta-blocker can be used if no alternative)
-Sick sinus syndrome
-Sinus bradycardia (HR less than 60BPM at start of treatment)
-Severe hypotension (systolic less than 100mmHg)
-Uncontrolled HF
Cautioned in:
-Diabetes
-Psoriasis
-Myasthaneia gravis
.
Key Beta-Blocker Drug Interactions
-ACEi and ARBs- enhanced hypotensive effect
-Parkinsons medication, Baclofen, ANxiolytics, Diuretics, MAOIs- enhanced hypotensive effect
-TCAs/mirtazapine/trazadone- increased postural hypotension risk
-Antidiabetic drugs- can mask hypoglycaemia
-CCBs- verapamil+BB can cause bradycardia and HF. Diltiazam can cause bradycardia and AV block. Nifedipine can cause HF and severe hypotension. Other CCBs can cause an enhanced antihypertensive effect.
-Amiodarone, flecainide and Quinidine- bradycardia and myocardia depression
-Clonidine- risk of withdrawal hypertension
-Corticosteroids, oestrogrens- hypotensive effect antagonised
-Digoxin-Reduce HR and prolong AV conduction time, increasing AV block and bradycardia risk. Monitor pulse carefully.
-NSAIDs- hypotensive effect antagonised
.
At what heart rate at the start of treatment would beta-blocker use be contraindicated?
Below 60 BPM
What are some drugs that interact with beta-blockers?
ACEis and ARBs
NSAIDs
Clonidine
Amiodarone/Flecainide/Quinidine
Corticosteroids
Oestrogens
Digoxin
Parkinsons medication
Baclofen
CCBs
Antidiabetic drugs
TCAs/mirtazapine/trazodone
What are some foods that can interact with anticoagulants?
Cranberry juice
Garlic
Ginger
Certain vegetables (asparagus, broccoli, cauliflower etc)
What can happen if you combine trimethoprim with methotrexate?
Bone marrow suppression- AVOID
Commonly Assessed Drug Interactions
-Aspirin/NSAIDs with Warfarin- increased bleeding risk
-Diuretic combinations
-Digoxin and quinidine- increased digoxin levels, may need to reduce by half.
-Digoxin and broad-spectrum antibiotics- can double serum digoxin levels
-Sildenafil and isosorbide mononitrate- Increased hypotensive effects
-Amiodarone and clarithromycin- prolonged QTc interval, avoid if possible
-Clarithromycin and simvastatin- increased myopathy risk, withhold simvastatin if clarithromycin taken.
.
What can happen if clarithromycin and simvastatin are taken together?
Increased myopathy risk
What can happen if digoxin is taken alongside quinidine?
Significantly increased digoxin levels, may need to reduce dose by up to a half
Alcohol-Drug Interactions
-Metronidazole- AVOID for up to 7 days after course finishes
-Warfarin- may affect INR and anticoagulation effect
-MAOI- can cause hypertensive crisis
-Mirtazapine or TCAs- increased sedative effect
.
Enzyme (P450) Inducers- Increases specific drug metabolism
Rachael’s Black Car Goes Putt Putt and Smokes
Rifampicin
Barbiturates
Carbamazepine
Griseofulvin
Phenytoin
Phenobarbitone
Smoking cigarettes
.
Enzyme (P450) Inhibitors- Decreases specific drug metabolism
Isoniazid
Cimetidine
Grapefruit
Disulfiram
Quinolones
Fluconazole
Sodium valproate
.
Remember: Lithium + thiazide diuretics can cause hyponatraemia.
What are some drugs that can cause fluid retention?
NSAIDs
Corticosteroids
Liver Disease and Drugs that May Cause Issues
-Amlodipine: may need a dose reduction
-Antacids- avoid in patients with fluid retention
-Anticoagulants- avoid if prothrombin time increased
-Carbamazepine- metabolism impaired, increased conc.
-Chloramphenicol- AVOID
-Clarithromycin/Co-amoxiclav/flucloxacillin- cholestatic jaundice, need to monitor
-Metformin- advised to avoid
-Metronidazole- reduce total daily dose to 1/3 if severe
-NSAIDs- AVOID
-Opioids- avoid or reduce dose
-Phenytoin- reduce dose
-Paracetamol- avoid large doses
.
Drug Induced Blood Dyscrasia and Agrunulocytosis
-Dyscrasia- a pathological condition of the blood, usually involving cellular elements.
Drugs that pose a risk:
-Aminosalicylates, such as sulfasalazine
-Carbimazole
-Methotrexate
-Clozapine
-Carbamazepine
-Captopril
-If a drug is given to a patient and the drug poses a risk, patient should be advised to monitor for unexplained bleeding, bruising, a sore throat, infections, fever and malaise.
.
What happens if you combine simvastatin and amlodipine?
Significantly increases simvastatin levels; 20mg is the max dose of simvastatin that should be used alongside amlodipine
Which juice should be avoided whilst taking warfarin?
Cranberry juice
What happens if a patient takes carbamazepine and apixaban?
Severe interaction; significantly decreases apixaban exposure, so increases blood clot risk
What can happen if you take digoxin and diuretics together?
Can cause hypokalaemia, which is an example of digoxin toxicity.
Why should the use of tetracycline antibiotics be avoided alongside lithium?
Risk of lithium toxicity.
What happens if you combine allopurinol and azathioprine?
Significantly increases azathioprine expoure, may need to reduce dose to 1/4 of usual dose.
What can happen if you combine colchicine with simvastatin?
Increased risk of rhabdomyolysis
What are they key interactions with amiodarone?
Decreased warfarin metabolism- bleed risk
-Increased digoxin levels
Amiodarone interacts with drugs that are commonly used alongside it, such as p450 inhibitors. For example, it decreases the metabolism of warfarin.
True or false?
True
What is the interaction between clarithromycin and simvastatin?
Increases simvastatin exposure= myopathy
What effect does baclofen have on antihypertensive drugs?
Enhances the hypotensive effect
Why are quinolone antibiotics cautioned in epilepsy?
They lower the seizure threshold
What can occur if you combine lithium and ACEi?
Increased chance of lithium toxicity
Why should lactulose and mesalazine not be taken together?
Latulose lowers stool pH and can prevent mesalazine from being released/working properly
At what CrCl would the use of bisphosphonates be contraindicated?
Below 30 ml/min
Colestyramine is contraindicated in complete biliary obstruction.
.
Amiodarone is contraindicated in complete AV block.
.
Ursodeoxycholic acid is contraindicated in patients with acute inflammation of the gall bladder.
What is the interaction between omeprazole/esomeprazole and clopidogrel?
Reduces the antiplatelet activity of clopidogrel
What is the interaction between theophylline and quinolones?
Can cause theophylline toxicity
REMEMBER: Do not take warfarin with _ juice
Cranberry
Digoxin + Quinine =??
Increased plasma concentration of digoxin
What can happen if a patient has glandular fever and is given amoxicillin?
They can develop a rash
Quinolone antibiotics can induce seizures, even in people without a history of seizures. This risk is increased y administration alongside which type of drug?
NSAIDs
What is the interaction between sumatriptan and tramadol/SSRIs?
Increases serotonin syndrome risk
What is the interaction between lithium and NSAIDs?
Decreases the excretion of lithium= toxicity
Which five drugs can reduce the effectiveness of tamoxifen?
Terbinafine
Paroxetine
Fluoxetine
Bupropion
Cincalcet
Which five drugs are key interactions with quinolone antibiotic?
-Drugs which prolong QT interval
-Corticosteroids- increase tendon damage risk
-NSAIDS- increased seizure risk
-Theophylline- can increase theophylline levels
-Methotrexate- can increase methotrexate levels
Amoxicillin can interact with methotrexate, by _ the clearance of methotrexate. Amoxicillin can also react with allopurinol and cause a _
Reducing
Rash
What is the interaction between fluoxetine and phenelzine?
Serotonin syndrome
What is the interaction between clonidine and propranolol?
Causes hypertension
What is the interaction between theophylline and ciprofloxacin?
Toxic levels of theophylline
What is the interaction between methotrexate and probenecid?
Significantly increase methotrexate levels
DAMN Drugs- These are drugs to be stopped in an AKI. What are these drugs?
Diuretics
ACEi/ARB
Metformin
NSAIDs
Which vitamin should not be taken alongside spironolactone?
Vitamin K
