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Drug interaction
An altered or modified action or effect of a drug as a result of interaction with one or more other drugs.
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Adverse drug reaction
Is an undesirable drug effect that ranges from mild untoward effects to severe toxic effects, including hypersensitivity reaction and anaphylaxis.
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Drug incompatibility
Is a chemical or physical reaction that occurs among two or more drugs in vitro (artificial environment)
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Pharmacokinetic interactions
Are changes that occur in the absorption, distribution, metabolism or biotransformation, and excretion of one or more drugs.
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Absorption
When a person takes 2 or more drugs at the same time, the rate of absorption changes. One can block, decrease, or increase rate of other.
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What are the 3 ways one drug can block, decrease, or increase the absorption rate of another.
1. By decreasing or increasing gastric emptying time. 2. By changing the gastric pH. 3. By forming drug complexes.
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Distribution
A drugs distribution to tissues can be affected by it's binding to plasma/serum protein.
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Drugs unbound to protein are____________.
Free active agents and can enter the body.
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Two drugs that are highly protein bound and are administered simultaneously can result in _____________.
Drug displacements
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Factors that influence displacement of drugs are...
(1) the drug concentration in the blood, (2) protein binding power of the drug, and (3) volume of distribution (Vd)
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Metabolism (biotransformation)
A drug can increase the metabolism of another by stimulating liver enzymes.
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Drugs that promote induction of enzymes are called _________
Enzyme inducers. (e.g. Barbiturates such as phenobarbital)
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Excretion
Drugs can increase or decrease renal excretion and have an effect on the excretion of other drugs.
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Pharmacodynamic interactions
Are those that result in additive, synergistic, or antagonistic drug effects.
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Additive effect
When 2 more drugs with similar action are administered, the drug interaction is called an additive effect and is the sum of the effects of the 2 drugs.
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Synergistic effect
When 2 or more drugs are given together, one drug can potentiate or have a synergistic effect on the other.
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Antagonistic drug effect
When 2 drugs that have opposite effects, or antagonistic effects, are administered together, each drug cancels the effect of the other.
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Food-drug interaction
Food is known to increase, decrease, or delay drug absorption. Food can bind with drugs, causing less or slower drug absorption. E.g. Tetracycline and dairy products.
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Drug-laboratory interactions
Abnormal plasma or serum electrolyte concentrations can affect certain drug therapies.
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Drug-induced photosensitivity
A drug induced photosensitivity reaction is a skin reaction that caused by exposure to sunlight
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Over-the-counter drugs
Drugs that are obtainable w/o a prescription, are found in most households.
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OTC drug categories
The FDA is responsible for categorizing OTC drugs.
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Category I
Drugs judged to be both safe and effective.
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Category II
Drugs judged to be either unsafe of ineffective; these drugs should not be included in nonprescription products.
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Category III
Drugs for which there are insufficient data to judge safety or efficacy
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Cough and cold medicine
Contain ingredients such as guaifenesin, dextromethorphan, pseudoephedrine, an analgesic, and an antihistamine.
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The FDA ordered removal of __________ from OTC cold remedies.
Phenylpropanolamine
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The nurse is aware that a former major ingredient in many OTC products is phenylpropanolamine, which is contraindicated for clients with all of the following conditions except
A. Heart disease
B. Thyroid disease
C. Diabetes mellitus
D. Kidney stones
Answer D rational: phenylpropanolamine, formerly in OTC cold remedies and weight-control drugs, may cause risk of hemorrhagic stroke in young women. May also cause psychosis, hypertension, renal failure, and cardiac dysrhythmias.
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What are good sources would you recommend to a client for information about OTC drugs?
A pharmacist, and the books Handbook of Nonprescription Drugs and Facts and Comparisons
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