Pharmacokinetics in Nursing

Pharmacokinetics in Nursing

Key Definitions

• Onset of Action

  • Definition: The onset of action is defined as the moment when the concentration of a drug at the site of action is sufficient to initiate a physiological response.

• Peak Action

  • Definition: The peak action is the time at which the drug reaches its highest concentration on the target receptor.

• Duration of Action

  • Definition: Duration of action refers to the total time that a drug has a physiological effect or action on the body.

Insulin as an Example

• Regular Insulin
  • Onset of Action: Approximately 15 to 30 minutes.
  • Peak Action: Around 1 hour, but can vary between 1 hour to 1.5 hours depending on different textbooks.
  • Duration of Action: Approximately 2 to 4 hours.

Nursing Considerations

• Patient Reassessment

  • It is crucial to reassess patients at the peak action of the drug, which for regular insulin is about 1 hour after administration.
  • This is critical to identify hypoglycemia, which is most likely to occur when the insulin is at its peak effectiveness.

• Sliding Scale Insulin

  • Example: If a patient has a blood glucose level of 180, and receives an order for 4 units of insulin, the nurse must ensure that the patient eats their food promptly after administration, as this aligns with the onset of action and peak effectiveness of insulin to avoid hypoglycemic reactions.

Delayed Reactions and Allergic Responses

• Potential for Delayed Reactions:

  • Some medications can have delayed allergic reactions, which may not be immediately apparent within the first thirty minutes.

• Example of Allergic Reaction:

  • Anecdote shared regarding anaphylactic reaction to Benadryl:
  • Symptoms experienced included loss of breath, swelling in the throat, and inability to speak.
  • Benadryl, typically given for allergies, has an onset of action that is estimated to be between 2 to 4 hours, with a duration of action lasting from 12 to 24 hours.

Implications for Medication Administration

• Long-acting Insulin (e.g., Lantus)
  • For a patient with high blood sugar, administering long-acting insulin (such as Lantus) is not suitable for quick action as:
  • It has a longer onset and duration, meaning it will not rapidly decrease elevated blood sugar levels.
  • Understanding the pharmacokinetics of medications is essential for safe and effective patient care.

Importance of Medication Knowledge in Nursing

• Comprehensive knowledge of the timing and effects of medications helps ensure:
  • Proper patient assessment and safety in administration.
  • Ability to prevent potential adverse reactions and therapeutic failures based on the pharmacokinetics of drugs.