Drug Interactions Flashcards by Kim Grace

Modification of the effects of one drug (object drug)
by the prior or concomitant administration of another
(precipitant drug

DRUG INTERACTION

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Object + Precipitant

DRUG INTERACTION

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Early recognition or detection can prevent:

Loss of therapeutic effect
Unexpected increases in pharmacologic activity
Toxicity

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Aplastic Anemia, Asthma, Cardiac Arrythmia, Critical/ICU patients, Diabetes, Epilepsy, Hepatic Disease, Hypothyroidsim

High risk associated with SEVERITY of the disease state being treated

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Autoimmune disorders, Cardiovascular Diseases,
GIT diseases, Infections, Psychiatric disorders, Respiratory disorders, Seizure disorders

High Risk Associated with Drug Interaction Potential of related therapy

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DRUG INTERACTION MECHANISMS (In Vivo)

Pharmacokinetic
Pharmacodynamic

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DRUG INTERACTION MECHANISMS (In Vitro)

Physicochemical (IV incompatibilities)

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chemical or physical interactions that occur in vitro

PHARMACEUTICAL INTERACTIONS

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aggregation, precipitation in solution, chemical deterioration or
decomposition

PHARMACEUTICAL INTERACTION

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PHARMACEUTICAL INTERACTION:

Potassium phosphate and calcium chloride in total
parenteral nutrition preparations (TPN) may form ________________, which will result in a _________ in the intravenous fluid
bag

calcium
phosphate; precipitate

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Drug disposition in the body

PHARMACOKINETICS

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Effect of a drug on the
ADME of another drug

PHARMACOKINETICS

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Seldom produces serious
clinical effects

PHARMACOKINETICS

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Often associated with
changes in plasma drug
concentration and altered
clinical response

PHARMACOKINETICS

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Most common Drug Interaction Mechanism

PHARMACOKINETICS

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Related to the pharmacologic
activity of interacting drugs

PHARMACODYNAMICS

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Amount of drug in blood
remains the same, but its effect
is altered

PHARMACODYNAMICS

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Change in gastric pH (antacid, alcohol, and food)

Alteration of DRUG ABSORPTION

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Changes in gastrointestinal motility/gastric
emptying time

DRUG ABSORPTION

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Damaged gastrointestinal mucosa

DRUG ABSORPTION

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Complexation and adsorption

DRUG ABSORPTION

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Sodium Bicarbonate + Ketoconazole

ABSORPTION (Changes in gastric pH)

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Sodium Bicarbonate + Ketoconazole

Object Drug:
Precipitant Drug:

Object Drug: Ketoconazole
Precipitant Drug: Sodium Bicarbonate

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Cyclosporine + Metoclopramide

ABSORPTION (Changes in gastrointestinal motility or gastric emptying
time)

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MANAGEMENT: Sodium Bicarbonate + Ketoconazole

Separation of doses by 2 or more hours

Cyclosporine + Metoclopramide Object Drug: Precipitant Drug:

Object Drug: Cyclosporine Precipitant Drug: Metoclopramide

MANAGEMENT: Cyclosporine + Metoclopramide

Renal function, serum creatinine, and Cyclosporine levels should be carefully monitored during concurrent therapy. Cyclosporine dosage should be adjusted as needed. Patients should be advised to notify their physician if they experience nausea, vomiting, diarrhea, abdominal pain, dizziness, fatigue, or headache

Digoxin + Vincristine

Damaged gastrointestinal mucosa (Drug Induced) (ABSORPTION)

Digoxin + Vincristine Object Drug: Precipitant Drug:

Object Drug: Digoxin Precipitant Drug: Vincristine (and other antineoplastic agents

MANAGEMENT: Digoxin + Vincristine

Digoxin serum levels and effectiveness should be monitored closely following the initiation or discontinuation of antineoplastic agents, and the dosage should be adjusted as necessary

Ciprofloxacin + Aluminum Hydroxide

Complexation and Adsorption (ABSORPTION)

Ciprofloxacin + Aluminum Hydroxide Object Drug: Precipitant Drug:

Object Drug: Ciprofloxacin Precipitant Drug: Aluminum Hydroxide

MANAGEMENT: Ciprofloxacin + Aluminum Hydroxide

Separation of two doses

Aspirin + Phenytoin

Alteration of DRUG DISTRIBUTION: displacement from protein binding sites

MANAGEMENT: Aspirin + Phenytoin

No action is requireD

Aspirin + Phenytoin Object Drug: Precipitant Drug:

Object Drug: Phenytoin Precipitant Drug: Aspirin

Phenobarbital Carbamazepine Phenytoin Rifampicin Tobacco smoke Alcohol (chronic)

Enzyme Induction (DRUG METABOLISM)

involves protein synthesis and therefore needs up to 3 weeks to reach maximal effect.

Enzyme Induction

example of Enzyme Induction:

CYP450 enzymes

___________ is the major metabolizing enzyme in Phase 1 Metabolism (Oxidation Process).

Cytochrome P450 enzyme

Paracetamol (prolonged use) + Carbamazepine

Enzyme Induction

Paracetamol (prolonged use) + Carbamazepine Object: Precipitant:

Object Drug: Paracetamol Precipitant Drug: Carbamazepine

Management: Paracetamol (prolonged use) + Carbamazepine

Monitor for decreased effectiveness of Paracetamol and signs of hepatotoxicity if Carbamazepine is used concomitantly, especially for patients receiving high-dose and/or chronic Paracetamol therapy

Cimetidine Erythromycin Ketoconazole

Enzyme Inhibition

may be due to competition on binding sites, so the onset of action is short (within 24 hours)

Enzyme Inhibition:

Fluconazole + Warfarin

. Enzyme Inhibition

Fluconazole + Warfarin Object: Precipitant:

Object Drug: Warfarin Precipitant Drug: Fluconazole

Management: Fluconazole + Warfarin

Consider 10-20% reduction in Warfarin dose with increased monitoring of anticoagulant response such as INR to guide further dose adjustment. Watch out for signs of bleeding.

Alteration of DRUG EXCRETION

a. Passive tubular reabsorption b. Competition at active transport site

Excretion and reabsorption of drugs occur in the tubules by passive diffusion, which is regulated by concentration and lipid solubility

PASSIVE TUBULAR REABSORPTION

Excretion and reabsorption of drugs occur in the tubules by passive diffusion, which is regulated by ________ and __________

concentration; lipid solubility

Aspirin + Sodium Bicarbonate

Passive Tubular Reabsorption

Aspirin + Sodium Bicarbonate Object Precipitant

Object Drug: Aspirin Precipitant Drug: Sodium Bicarbonate

MANAGEMENT: Aspirin + Sodium Bicarbonate

Patients treated chronically with urinary alkalinizers and large doses of salicylates (i.e. 3 g/day or more) should be monitored for potentially-diminished or inadequate analgesic and antiinflammatory effects, and the salicylate dosage adjusted if necessary.

Competition at the active transport site: Active tubular secretion occurs in the_________

proximal tubules

Competition at the active transport site: When another drug has a competitive reactivity ot the protein responsible for active transport of another drug, it may _______________ that drug’s excretion, ___________ its reabsorption and concentration, and hence its toxicity.

reduce; increasing

Probenecid + Methotrexate

Competition at the active transport site

Probenecid + Methotrexate Object: Precipitant:

Object Drug: Methotrexate Precipitant Drug: Probenecid

MANAGEMENT: Probenecid + Methotrexate

a reduction in methotrexate dosage may be needed, and the patient should be closely monitored for signs and symptoms of bone marrow suppression, hepatotoxicity, and nephrotoxicity. Patients should be advised to promptly report symptoms including fever, chills, sore throat, bruising, bleeding, stomatitis, malaise, shortness of breath, lower extremity edema, jaundice, or change in stool or urine color to their physician.

Most significant are those involving drug _____________ and the least significant are those involving drug ____________.

metabolism; distribution

INCREASE in drug concentration = __________

TOXICITY

DECREASE i drug concentration = __________

TREATMENT FAILURE

Increase in bioavailability, effect of an enzyme inhibiting drug, ____________ in excretion

decrease

Decrease in bioavailability, effect of an enzyme inducing drug, _____________ in excretion

increase

PHARMACODYNAMIC INTERACTIONS

1. Additive/Synergistic effect 2. Antagonistic effects 3. Indirect effects

Benzodiazepines + Sedating antihistamines

Additive/Synergistic effects

Propranolol + B2 Agonist

Antagonistic effects

Digoxin + Loop Diuretics

Indirect effects

Contraindicated/ Avoid combination

Major/ Consider therapy monidfication

Moderate/ Monitor therapy

Minor/ No action needed

Unknown/No known interaction

Drug Interactions Flashcards

(73 cards)