Drug Effects, Interactions, Allergies and Antimicrobials

Core Drug Actions, Responses, and Safety Concepts

Administering medications safely requires the practical nurse to understand how drugs behave in the body and what responses to anticipate. A therapeutic medication effect is the expected, intended, and desirable physiological response to a drug. To ensure therapy is working as planned, the licensed practical/vocational nurse (LPN/VN) collects data on vital signs and symptoms, compares these findings with the medication's expected effect, and reports any concerns to the registered nurse (RN). Medication timing is defined by key pharmacological benchmarks: the onset of action is the time required after administration for a drug to produce its initial therapeutic response; the peak drug level is the highest concentration of a medication in the bloodstream following administration; and the duration of action is the length of time that a medication continues to produce its therapeutic effect.

Not all client responses are therapeutic. Side effects are unintended, often predictable effects that can occur at therapeutic doses, though they are not always unavoidable. In contrast, adverse drug reactions are unintended, harmful responses to a medication that may require clinical intervention. When a medication accumulates to dangerous levels, toxic medication effects occur. These toxic effects can result from an overdose or drug accumulation, including accumulation caused by impaired metabolism or excretion. Less commonly, an idiosyncratic drug reaction may occur, which is an unpredictable, individual-specific response that differs from expected pharmacological actions. If a client develops acute respiratory depression after an opioid, the LPN/VN stops or holds the opioid, calls for emergency help and the RN, supports breathing, and administers naloxone if authorized by an order or protocol and state scope.

Safe drug administration also requires recognizing clinical boundaries before a dose is ever given. An absolute contraindication is a condition or circumstance in which a medication should not be given because its risks are unacceptable. If a documented contraindication is identified during pre-administration checks, the LPN/VN withholds the dose and promptly notifies the RN or prescribing provider. A precaution, on the other hand, is a medical condition requiring close observation, monitoring, or dosage modification when administering a medication. For example, impaired kidney or liver function can alter the excretion or metabolism of certain medications; such client conditions serve as precautions requiring closer monitoring or a dosage adjustment to prevent drug accumulation and toxicity.