Drug Interactions Flashcards
(51 cards)
How many drugs are people likely to receive in the hospital, for what?
Patients often receive more than 20 drugs in hospital
Control: pain, anesthesia, muscle relaxant, blood pressure, control infection, anti-anxiety
Drug interactions using prescription drugs?
Over the counter medication, with prescription or herbal remedies, (drug interactions could be dangerous)
What is the relationship between the number of drugs and side effects due to interactions?
Amount of side effects goes up as you increase the amount of drugs
Not too significant side effects with 0-5 drugs but goes up for 6-10 drugs and then significantly higher for 11-15 drugs and very high for 16-20 drugs
Why is poverty a major risk factor for drug interactions?
buy a lot of things OTC or try herbal remedies, take some stuff without consulting a doctor, so they are more at risk since they don’t have the money to ask a professional
Are drug interactions positive or negative?
Both, We usually look at the negatives since we want to avoid them, and some can lead to death
There are some positive ones that give a benefit when taking together
What does beetroot do?
Beetroot: urine turns red, the dye in beets is not absorbed
Red wine interactions?
Red wine: over 1000 chemicals, some interact, some can give headaches on their own like tyramine
What are factors influencing drug interaction outcomes?
Patient factors: genetics, disease, diet, environment, smoking, alcohol
Drug administration: dose, duration, dosing times (the times you take the different drugs, A vs B first) , sequence, route, dosage form
There is a high variability in drug interactions between people
Just because person A can take a certain combination doesn’t mean person B will be able to take that combination, it has to be varied for each person individually
Classification of drug interactions: Consequence?
- Beneficial or adverse
Classification of drug interactions: site?
- External or internal (usually internal)
Classification of drug interactions: Mechanism?
- Pharmacodynamic (two drugs act on same receptor site to magnify or decrease an effect)
- Pharmacokinetic (increase or decrease metabolism)
- Physiological (increase or decrease a physiological response)
Types of interactions? (4)
- Additive (drugs d o a similar thing, 1+1=2)
- Synergistic (one drug magnifies the effect of another (1+1=3))
- Potentiation (one drug does nothing by itself but can magnify the effect of another one) (1+0=2)
- Antagonism (one drug antagonizes the effect of another drug) (1+0= 0.5)
Pharmacokinetic mechanisms of drug interactions?
One drug can alter the absorption, distribution, metabolism, or excretion of another drug
Alter blood concentration of a given drug, more or less of it available in the blood
Pharmacodynamic mechanism of drug interactions?
Two drugs are acting on the same site, one drug can compete with it, block it, alter it
Modulate drug effect at a given plasma concentration (the blood concentration stays the same but the effect on receptors is different for the same concentration)
Altering the plasma concentration of a drug? (pharmacokinetics
- Get a higher concentration of the drug, the level is closer to the toxic level, more side effects
- Get a lower concentration of the drug, there will not be enough for an effective level
How can drug absorption be altered?
Gastric pH will alter the absorption of some drugs (tetracycline, antibiotic, on empty stomach good absorption, but with milk the calcium carbonate binds to the tetracycline so it will not be absorbed)
Calcium Carbonate inhibits Thyroxine absorption (girl separated her doses morning and night)
What drugs affect the gastric pH?
- Omeprazole, lansoprazole, H2-antagonists alter gastric pH, reduce absorption of ketoconazole, delavirdine
What factors (3) effect drug absorption?
Transit time, absorptive surface area, complex formation
Some people have reduced absorptive surface area due to diseases like inflammatory bowel disease
Transit time altered if someone has diarrhea the blood can pass through very rapidly
A complex formed in the intestine, so the drug can’t be absorbed
What do p-glycoproteins do?
P glycoproteins prevent drug from getting into the portal vein, kicks it back out to intestinal lumen
(prevents drug accumulation in cells)
Drug effect on p-glycoproteins and absorption?
If a drug inhibits the p-glycoprotein, more of another drug will be absorbed into the blood, can get an overdose of the second drug
Can also upregulate the p glycoprotein, so have less of a second drug in the blood, so it will no longer be effective
What drug interactions can alter distribution?
Unbound drugs are also the ones that can be metabolized
Drug interaction regarding plasma protein binding
A second drug kicks the first one off of plasma proteins so there is much more free drug in circulation and there can be an overdose of it, pretty rare in reality, usually enough plasma proteins and they don’t kick each other off
(usually a balance of unbound to plasma protein bound drugs)
What are the 2 main cytochrome P450s that break down drugs, how can they be altered by drug interactions?
P450 enzymes, CYP3A4, CYP2D6 very important to metabolize drugs
For each of the different types of P450 enzymes their activity can be altered by many things, inhibition, it can be induced, inhibited, polymorphisms for different people
Ketoconazole (anti-fungal) drug interaction making it less active?
It is metabolized by many CYP450s, CYP3A4
Enzyme inhibition,
Since Ketoconazole needs to be broken down to its active intermediate to cause an effect, there is decreased amount of the effective drug
