Drug interactions Flashcards
What is a DI?
When the effects of one drug are altered by another substance like drugs, food, herbals, alcohol, nicotine, and disease states.
What is a DDI?
when a substance precipitating the change in effect is a drug
What are the most common DDI causing drugs?
NSAIDs and Digoxin and Warfarin
What are high risk conditions for DDIs?
aplastic anemia, asthmas, cardiac arrhythmia, diabetes, seizure disorders, hepatic disorders, hypothyroid, autoimmune diseases, infection, respiratory disorders.
What are the 4 high risk populations of DDI?
Elderly, critical care patients, patients with complications, and surgical patients.
What is a PK DDII?
It influences the disposition of a drug in the body and effects ADME. They frequently cause marked shifts in serum drug concentrations and altar clinical response.
What is a PD DDI?
differences in drugs response at given drug concentrations in the plasma. It happens at the levels of binding sites or secondary messenger systems. Usually associated with synergism, antagonism, or altered transport across cell membranes. They affect organ systems and receptor sites.
What are examples of causes of DDIs that can happen prior to administration?
a change in absorption caused by; chelating agents, changes in gastric PH, alterations in GI motility, modify of PGP, alterations in intestinal flora from antibiotic use
How can phenytoin become a DDI when mixed with dextrose?
a precipitate forms and the phenytoin becomes an insoluble salt that is no longer dispersed throughout the solution and becomes ineffective
What happens when aminoglycosides are mixed with beta lactam antibiotics?
It reduces antibiotic efficacy
What drugs do iron, magnesium, calcium, and aluminum decrease the absorption of?
These are chelating agents, and it affects fluoroquinolones, and tetracycline. They should be given at least two hours apart from chelating agents.
What drugs do cholestyramine bind to and decrease the absorption of?
Raloxifene, thyroid hormones, and digoxin
what drugs can PPI interact with
it neutralizes the stomach acid and drugs that require acid for absorption will be decreased like, ketoconazole, digoxin, iron salts, and ampicillin
How do laxatives decrease the absorption of certain drugs?
It causes an increase in GI motility and drugs that require a longer absorption time will be absorbed too fast.
What PGP drugs are affected by blocking of pgp?
steroids and digoxin, and blocking can cause increased toxicity of those drugs
What drugs do antibiotics decrease the absorption of?
Oral contraceptives by decreasing gut flora
What is an example of two drugs that fight for the same binding site and become displaced?
Warfarin and diclofenac, results in a increased level of warfarin and could cause serious affects like bleeding.
What are CYP 450 enzyme inducers
Stimulates enzyme production which leads to increased metabolism and decreased drug effect
What are CYP 450 inhibitors?
inhibits enzyme production which can leads to decreased drug metabolism and increased drug effect & toxicity.
What are examples of enzyme inducers?
barbiturates, carbamazepine, griseofulvin, phenytoin, and rifampin.
Is ritonavir a enzyme inhibitor or inducer?
It could be both depending on the situation.
What class of drugs are most susceptible to enzyme induction?
CYP3A4 and CYP2C9
Inhibitors of which class increases theophylline toxicity?
CYP1A2
Inhibitors of which class increase phenytoin oral anticoagulation toxicity?
CYP2C9
What is an example of two drugs that use the same transport system to be secreted from renal tubule cells?
methotrexate and ibuprofen- could result in decreased excretion of methotrexate and cause toxicity.
Alteration in urine PH affect which two reabsorption pathways?
active and passive tubular reabsorption
if the pH of the urine is _______ the reabsorption of acidic drugs is reduced
alkaline
if the pH of the urine is _______ the reabsorption of basic drugs is reduced
acidic
what two types of drugs alkalinize the urine and decrease the rate of salicylate reabsorption and increase its excretion?
Thiazide diuretics and sodium bicarb
What are synergistic effects?
combined drug effects that produce a greater response than the combined two drugs 1+1=3
What are additive affects?
combined drug effects produce a reaction that is equal to the combination of the drugs (also called summative) 1+1=2
What is potentiation?
One drug increases the effect of the other. It may result in increased toxicity.
Beta blockers, ace inhibitors, and nitrates can all reduce BP causing a combined _____ effect
synergistic
What are two examples of Additive drug interactions?
combinations of drugs that prolong the QTc interval create ventricular arrythmias or combining drugs with hyperkalemic effects leading to hyperkalemia
What are two examples of antagonistic drugs
NSAIDS may inhibit antihypertensive drugs like ACE inhibitors OR benzos inhibited by theophylline
What is a beneficial antagonist?
Naloxone used in opioid overdose
What is a harmful antagonist?
a beta 1 agonist will have reduced bronchodilation with a non-selective beta blocker
What is a prescribing cascade?
When ADRs of a drug aren’t recognized and a second drug is prescribed to tx the side effects. It may increase the risk for new ADRs or increase the severity of the same ADR
What is combined toxicity?
When two or more drugs have a toxic effect on the same organ and increase the risk for organ damage
When penicillin, tetracycline, erythromycin, levodopa, and phenytoin and digoxin are taken with food it ________ the absorption
decreases
When spironolactone, Griseofulvin, and itraconazole are taken with food it _______ the absorption
Increases
Taking ketoconazole with cola products leads to-
prolonged serum levels of the ketoconazole
What foods are high in vitamin and decrease warfarin effects?
Alfalfa tabs, broccoli, brussels sprouts, cabbage, cauliflower, green leafy vegetables, green tea, liver, soybeans, veggie oils, and watercress.
What foods and vitamins cause increased levodopa metabolism and have decreased blood levels of dopamine and Anti parkinsonism effects
Vitamin B6, avocados, beans, peas, sweet potatoes. bacon, beef liver, pork, tuna
What can calcium interact with to do reduce bioavailability?
Fluoroquinolone antibiotics and phenytoin- decreased antibiotic activity and causes a loss of seizure control
What drugs cause weight gain when patients with diabetes take them?
TCAs, mirtazapine, paroxetine, clozapine, olanzapine, quetiapine, risperidone, lithium, valproic acid
What drugs should you avoid if you have hypertension?
Venlafaxine, duloxetine, and bupropion because they increase BP
What drug should you avoid if you have epilepsy?
Bupropion
What drugs should you avoid with Parkinson’s disease?
Risperidone, and conventional antipsychotics
What drugs should you avoid with Alzheimer’s disease?
Antipsychotics, TCAs, Paroxetine, clozapine, and olanzapine
What drugs should you remember are high risk for DDIs?
anticonvulsants, antibiotics, antidepressants, digoxin, warfarin, amiodarone
What resources can you use to check for DDI?
epocrates, pharmacist, colleague, computerized alert system, and package inserts
Where should you report ADE?
MedWatch for serious reactions and drug manufacturer for nonserious reactions
Where can you report vaccine ADE?
VAERS
Describe the process that is required by the Food and Drug Administration to move a drug from a candidate molecule to a drug approved for clinical use
IND app-> Clinical trials -> NDA submission and approval
Describe a rational course of action for the situation where there is a high probability that two or more drugs of a patient’s regimen are interacting with resultant deleterious effects.
The first step is to avoid DDI’s whenever possible: consider who are high-risk patients; which drugs are considered high-risk for DDI’s; report any known or suspected DDI to the pharmacy and appropriate organization
Explain what is meant by “Post-Market Surveillance” and the role of advanced practice nurses in this process
Phase IV, The FDA seeks voluntary reporting of ADRs from healthcare professionals on MedWatch. It is important for detecting ADRs that are uncommon and unlikely to be found in clinical trials
