Med/Surg Pharm Ch. 6-8

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When a patient is taking two medications, onde drug may intensify the ffects of the other

These effects can result in increased therapeutic effects, or in increased adverse effects

When taking two drugs, and they inhibit the action of each other

These effects can reduce the therapeutic effects of one (or both) drugs which is detrimental, or they can reduce the adverse effects - like naloxone and morphine

Direct chemical or physical interaction - when combining to meds in an IV bag they may react and form a precipitate, this same type of reaction can occur when the drugs are mixed together in a patient

Pharmacokinetic interactions - may alter the absorption, distribution, metabolism, or excretion
Absorption - one drug may elevate the pH altering with the ionization of a drug in the stomach, Laxatives can lessen absorption time in the intestine, Opiods can decrease GI motility causing an increase in absorption time, decresing blood flow to an area (epinephrine and local anesthetics) decrease absorption

Distribution - through either competition for protein binding or alteration of extracellulat pH (by doing this drugs may be pulled out of cells due to the partitioning effect)

Metabolism - (one of the most important and complex mechanisms by which drugs interact)
Inducing - some drugs induce the synthesis of CYP isoenzymes

Excretion - glomerular filtration may be reduced by drugs that decrease cardiac output, by altering urinary pH one drug can alter the ionization of another thereby increasing or decreasing tubular filtration

It is when a drug causes the production of more isoenzymes in the liver - i.e. phenobarbital increases the enzyme that metabolizes it and other drugs

it takes 7-10 days for the increase to develop and 7-10 days for it to be relieved

Also if a pt is on an inducing agent, and is then withdrawn from it, the pt's other meds may need to be lowered to inhibit toxicity

Pharmacodynamic interactions:
1. interactions in which the interacting drugs act at the same site
2. interactions in which the interacting drugs act at seperate sites

same receptor - always inhibitory
Seperate sites - even if the drugs have different mechanisms of action and act at different sites they may still influence the same physiologic process

Drug-Food interactions:
Taking tetracycline antibiotics along with calcium forms a precipitate that cannot be absorbed. High fiber foods can slow or reduce absorption with some drugs (digoxin)

Grape fruit juice inhibits metabolism by inhibiting CYP3A4

True

False, they are generally predictable

An uncommon drug response resulting from a genetic predisposition

an iatrogenic disease is a syndrom that is drug induced but mimics a naturally occuring pathology, i.e. developing parkinson like signs from certain chemotherapy drugs

Jaundice, dark urine, light-colored stools, nausea, vomiting, malaise, abdominal discomfort, loss of appetite

Refers to the ability of some drugs to prolong the QT interval which is a sign of dysrhythmias. Women are at greater risk with these drugs b/c their QT interval is naturally longer than in men.

Signs of liver toxicity: jaundice, dark urine, light-colored stools, N&V, malaise, abdominal discomfort, loss of apetitie

For kidneys creatinine tests should be performed

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