hi my name's amanda and i'm a pharmacist today i'll be talking about drug interactions and if you find this video useful please press the like button and subscribe to my channel and share it with others who may find it helpful too thanks i really appreciate it so we'll begin with what is a drug interaction a drug interaction is a reaction that occurs between a drug and another substance that causes a change in the action or side effects of the drug drug interactions can cause a decrease in efficacy or how well the drug works and an increase in side effects and toxicity of a drug and there are different types of drug interactions which we'll look at in more detail with some examples there are drug drug interactions drug dietary supplement interactions drug nutrient or drug food interactions drug disease interactions and drug laboratory interactions before we get into the specific types of drug interactions we'll look briefly at the causes of drug interactions they can be pharmacodynamic or pharmacokinetic in nature pharmacodynamic drug interactions occur when the effect of a drug is changed by the presence of another substance acting at the same place and these effects can be additive effects meaning the total effect is the same as the sum of each drug they can be synergistic effects meaning the total effect is greater than the sum of each individual drug or there can be antagonistic effects this means the action of the drug would be diminished or there are pharmacokinetic drug interactions and these occur when the concentration of a drug is changed in the body due to the change in clearance peak levels things like that now these type of drug interactions are complex and difficult to predict because they are usually of unrelated pharmacologic actions we'll look now at the specific types of drug interactions we'll begin with drug drug interactions this is the most common type of drug interaction and basically it's a reaction that occurs between two drugs possible effects of drug drug interactions depending on the specific drugs involved there can be an increase of drug effect this can lead to toxicity there can be a decrease in drug effect this may lead to ineffectiveness or an increase in side effects now we'll look at some examples of drug drug interactions warfarin with aspirin there can be an increased bleeding risk ace inhibitors if you remember these are the drugs with the suffix pril like lysinopril with spironolactone and this can lead to hyperkalemia which are high potassium blood levels there's digoxin with amiodarone or varapamil can lead to increased digoxin levels risk of digoxin toxicity fluoroquinolones these were the antibiotics then then floxacin like ciprofloxacin combined with theophylline can cause an increase in theophile theophylline levels which can increase the risk of theophilin toxicity warfarin plus fluoroquinolone or macrolide antibiotics like azithromycin there can be an increased bleeding risk and the azo antifungals plus statins there can be an increased statin side effect risk and there are many other examples of drug interactions but these are just a few common ones now we'll look at drug dietary supplement interactions and this is a reaction between a drug and a dietary supplement in a dietary supplement we can consider that a vitamin mineral botanical enzyme something like that that's taken in a pill form some examples of drug dietary supplement interactions anti-anti-depressants combined with st john's wort that can cause too much serotonin which can lead to something known as serotonin syndrome which increa includes symptoms like high blood pressure headaches seizure irregular heartbeats and things like that um warfarin with combined with ginkgo can cause an increased risk of bleeding and there are many other supplements that interact with warfarin and benzodiazepines such as alprazolam with kavakava can cause an increased risk of drowsiness next are drug nutrient interactions this is a reaction between a drug and a nutrient and a nutrient is a vitamin or mineral that's in food and there is some overlap with drug supplement interactions here because the vitamins and minerals as supplements will also interact with with these drugs as well so there's warfarin with vitamin k rich foods this would be like dark leafy greens or vitamin k supplement it causes actually an increase in clotting and would be a decrease in the effectiveness of the warfarin tetracyclines plus calcium-rich foods such as milk or calcium supplements you'll get a decrease in the tetracycline levels fluoroquinolones like the ciprofloxacin combined with calcium magnesium iron or aluminum this would be like an antacid or something like that or in a food they bind to the antibiotic and cause a decrease in levels of the antibiotic ace inhibitors like lysinopril with potassium causes an increased risk of the hyperkalemia which are the high potassium blood levels now we'll look at drug food interactions this is a reaction between a drug and a food and first one we'll look at this is an older reaction and these drugs you don't see them very often but it is a commonly known drug food interaction that is the mayo inhibitors some examples of those are phenolsene or celegiline and combined with tyramine which is a amino acid in aged or fermented foods such as wine cheese or cured meats it can cause an increase in blood pressure to dangerously high levels and then another common drug food interaction that that you do see now is the hmg coa reductase inhibitors like the statins like atorvastatin with grapefruit this can cause an increase in statin levels and increase in the side effects of the statins and i have a chart here of some of the common drugs that interact with grapefruit and these there are several because these drugs are metabolized by the sip 3a4 liver enzyme which grapefruit inhibits so that's the mechanism of that interaction alprazolam amiodarone carbamazepine erythromycin and clarithromycin cyclosporin colchicine phelodipine verapamil warfarin those are a few other medications that also have the grapefruit interaction now we'll look at drug disease interactions this is a reaction between a drug and a disease some examples here beta blockers such as propranolol and these can sometimes worsen asthma if they're the non-selective beta blockers nasal decongestants such as pseudoephedrine these can increase blood pressure to dangerously high levels in patients who already have high blood pressure aspirin or the nsaids they can worsen peptic ulcer disease or stomach problems nsaids and they can also they can cause fluid retention which can worsen congestive heart failure and steroids such as prednisone these can increase blood sugar levels which can worsen diabetes control and last we'll look at drug laboratory interactions this is a reaction between a drug and a lab result the pharmacologic action of a drug can change the result of a lab test but the change may be accurate and not interfere with the lab test like for example levothyroxine can increase thyroid levels so this really isn't a drug lab interaction but a true drug lab interaction occurs when the drug alters a test specimen or interferes with the testing reagents and this could be something like a false elevation in levels or false positives or negatives the most common drug lab interactions are with urine specimens and just one little example here cephalosporin antibiotics can alter urine glucose and ketone tests so now we'll just look at a summary and some key points a drug interaction is a reaction that occurs between a drug and another substance that causes a change in the action or the side effects of the drug and drug interactions can cause a decrease in the effectiveness of the drug or an increase in side effects and potential toxicity and the types of drug interactions there are drug drug drug dietary supplement drug nutrient and drug food drug disease and drug laboratory thanks for watching please like and share this video with others who may find it helpful and please subscribe to see more of my drug information videos thank you you