Pharmacodynamics - Types of Secondary Effects

adverse drug event

• any effect other than the therapeutic effect

• can be harmful or harmless depending on the situation

side effects

• minor adverse effects

• often harmless; may be harmful

• ex: Benadryl (allergy meds) but used for drowsiness

toxic reactions

• results from overdose or buildup of med in the blood or secretion

• ex: kidneys not working well, it’s getting backed up, can damage organ function (monitor!)

tolerance

• when a pt develops a decreased response to a med and requires a higher dose to obtain therapeutic effects

• body keeps asking for more dose to get back to the desired therapeutic effects

allergic reactions

• result from an immunologic response to a med to which the pt has been sensitized

• ex: A patient takes penicillin and within minutes develops hives, swelling of the lips, and difficulty breathing

compatibility

• drug will precipitate from solutions, or chemically inactive, if mixed with other med

• ex: A nurse mixes phenytoin with dextrose IV solution, causing the medication to precipitate, so the drugs must be administered separately

• this is why sometimes 2 meds can’t go in the same IV or you have to wait half an hour before administering the other

idiosyncratic interaction

• a rare unpredictable, and often severe adverse response to a drug or substance that is unique to an individual and not typically observed in the general population

• ex: A patient receives codeine and experiences severe respiratory depression, a type of reaction not seen in most patients

synergism

• occurs when a medication’s effects are altered by the concurrent presence of other medications or food

• drug effects increase

• ex: A patient takes alcohol with benzodiazepines, causing extreme sedation

antagonism

• occurs when a medication’s effects are altered by the concurrent presence of other medications or food

• drug effects decrease

• ex: A patient takes naloxone, which reverses the effects of morphin

cumulative

• the clinical or immunologic impact after the second dose is greater than after the first dose because the effects of both doses add together, producing a stronger overall response

• ex: A patient receives a second dose of a vaccine, and the immune response is stronger than after the first dose because the effects of both doses add together