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30 Cards in this Set
- Front
- Back
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What are the two ways in which drug interactions can occur?
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Drug-drug
drug-food |
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Name the 2 types of drug-drug interactions?
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pharmacokinetic
pharmacodynamic |
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Define a pharmacokinetic drug-drug interaction.
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directly alter those physiological processes which are involved in the absorption, distribution, biotransformation and/or elimination of drugs; indirectly (secondarily) change intensity of drug action
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Define a pharmacodynamic drug-drug interaction.
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direct alteration of pharmacological effects of drug at common receptor sites; indirectly (secondarily) by acting on systems (organs, tissues, receptors) different from those of the primary drug
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What are some common pathological states that require a multiple drug treatment plan?
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hypertension
heart failure cancer pain |
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What are possible outcomes of drug-drug interactions? What is the DESIRED outcome?
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increased/decreased therapeutic effect
increaased/decreased toxicity Goal: increased therapeutic effect with reduced ADRs |
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Name 5 pharmacokinetic drug-drug interactions that can occcur taking drugs orally (po):
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1. formation of unabsorbable complex with metal ions
2. formation of unabsorbable complex with other drugs 3. alteration of GI flora 4. increased GI motility 5. decreased GI motility |
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The relationship between warfarin and phenylbutazone illustrates what?
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"displacement" drug-drug interaction: pbz displaces warfarin from plasma proteins, increasing its plasma concentration and thus its activity
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What leads to an increase in cytochrome p450 (cyp)? What is this called? What effect does this have on drug activity? Name examples of drugs that cause this.
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results from prolonged exposure to certain chemicals; called enzyme induction; leads to shorter T1/2B and reduced pharma activity
e.g. barbituates, anticonvulsants, rifampin |
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What leads to an decrease in cytochrome p450 (cyp)? What is this called? What effect does this have on drug activity? Name examples of drugs that cause this.
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this is enzyme inhibition; leads to reduced biotransformational activity; longer T1/2B and increased pharma activity;
e.g. cimetidine, ciprofloxacin, oral contraceptives, fluoxetine |
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Why must physicians be careful when prescribing fluoxetine (prozac)?
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strong inhibitor of cytochromep450;
when added to therapy with other anti-depressants can cause toxic increase in blood levels of those other drugs must decrease dosage by %25 and monitor blood levels |
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What is the effect of diuretics on Lithium?
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diuretics > decreased Na+ > retention of Lithium > increased likelyhood of ADRs
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What are the two types of pharmacoDYNAMIC drug-drug interactions?
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enhancement
antagonistic |
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Define "enhancement" and name the two outcomes
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combining drugs with similar pharmicologic activty; can have an additive effect or a potentiating effect.
*this latter is greater than the sum of the parts and usually involves two drugs with different mechanisms |
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What is an MAOI? Are they strong? Give an example of one.
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Monoamine oxidase inhibitors; powerful anti-depressants; e.g. tranylcypromine
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What types of patients should not take MAOIs?
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those over 60
those with heart disease and/or hypertension |
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Patients on MAOIs are at increased risk for the following (4):
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hypertension (amphetamines, L-dopa)
hyperpyrexia (meperadine & other narcotics) psychosis (dextromethorphan) serotonin syndrome (fluoxetine) |
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What is Serotonin syndrome? What causes it?
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hyperstimulation of the serotonin system; can be caused by d-d interactions such as fluoxetine + MAOIs
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What are the effects of Serotonin syndrome?
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disseminated intravascular coagulation (DIC)
hyperthermia tachycardia acute renal failure diaphoresis shivering tremor myoclonus confusion & delirium |
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Antagonistic pharmacodynamic drug-drug interactions can be defined as:
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combination of drugs with opposite pharmacologic effects
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What would be an example of a desired therapeutic antagonism?
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post-op cholinergic drug admin to reverse effect of muscle relaxant giving during surgery
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What would be an example of using antagonism during an emergency?
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naloxone for narcotics
flumazenil for benzodiazepines |
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Define "cross-tolerance".
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reduced response to a drug having a molecular structureaction similar to the drug which caused the tolerance
* could be up or down regulation |
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Give an example of an undesired therapeutic antagonism.
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thiazidide diuretics induced hyperglycemia counteracts insulin-induced control of blood glucose
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Name several interactions between drug and food:
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-formation of chelate (e.g. tetracycline with Ca2+ in dairy)
-reduced absorption -increased absorption |
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How could certain foods increase drug absorption?
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drugs that undergoe significant hepatic first pass effects (propanolol); food provides substrate to liver allowing more drug to enter circulation
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What role does pH play in drug-food interactions?
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some foods can alter pH which in turn can alter drug absorption;
e.g. antacids increase pH and decrease absorption of ketoconazole |
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What effect does grapefruit juice have on drug activity?
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enzyme inhibition;
reduced biotransformational activity |
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What dietary restrictions should be considered in patients on MAOIs?
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anything containing tyramine
-causes rapid increase in blood pressure |
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What are the 7 ways a physician can reduce the frequency/severity of unwanted d-d interactions?
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1. complete understanding of all prescribed drugs
2. know patient risk factors 3. inform patient of possible ADR 4. educate patient on "why", "how" 5. monitor multi-drug therapies 6. consult all members of HC team 7. respond to HC team about potential d-d interaction |
