Final answer:
Medication indicated as PRN is given 'As needed' and it depends on the individual circumstances of the patient. PRN is not based on a set schedule, but rather a response to symptoms, reflecting the pharmacological properties such as half-life and whether the medication is dose or time dependent.
Step-by-step explanation:
If medication of a patient or a resident is indicated as PRN, it is given As needed. PRN is an abbreviation from the Latin phrase “pro re nata,” which translates to 'as the situation demands.' This means that the medication is not to be taken on a regular schedule but rather only when certain conditions are met, such as the onset of symptoms or pain. For example, pain relief medication for chronic conditions might be prescribed as PRN since the intensity of pain can vary day to day.
The decision to use drugs on a PRN basis is often related to their pharmacological properties, such as half-life and whether the drug's effectiveness is dose dependent or time dependent. A short half-life means the drug is metabolized quickly and must be administered more frequently to maintain its therapeutic effect. On the other hand, a drug with a long half-life stays in the system longer, which can be advantageous for maintaining stable blood levels but may also prolong the presence of any toxic side effects. Medications can also differ in their efficacy based on the dosage and duration—some are more effective at high doses over short periods (dose dependent), while others work better when maintained at optimal levels over extended periods (time dependent).