Pharmacology: Allergic Reactions and Interactions

Allergic Reactions

• Allergic reactions are immunologic responses to drugs, which may vary in severity.
• Anaphylactic reactions are severe and often manifest immediately after drug administration.
• Common mild allergic reactions include:
  • Pruritus (itching)
  • Rhinitis
  • Angioedema
  • Wheezing (during exhalation)
  • Stridor (during inhalation)
  • Nausea (vomiting)
  • Skin rash

Drug Interactions

• Drug interactions can occur as:
  • Drug-to-drug interactions: Effects may be potentiating (increased effect) or inhibiting (decreased effect).
• Potentiating effect demonstrates that the response of one or both drugs is amplified.
• Inhibiting effect indicates that one of the drugs reduces the effect of the other.

Drug Toxicity

• Drug toxicity results from overdose, use of external drugs internally, or accumulation due to impaired metabolism or excretion.

Drug Tolerance

• Drug tolerance occurs when a drug elicits a weaker response, necessitating higher doses to achieve the same therapeutic effect.
• First-pass effect: A significant portion of orally administered drugs is metabolized in the liver, reducing bioavailability.

Drug Metabolism and Excretion

• Bioavailability is the percentage of administered drug available for activity after metabolism.
• Drug distribution involves drug movement from blood to target tissues, facilitated by protein binding.
• Plasma proteins like albumin and lipoproteins play crucial roles in drug distribution.
• Kidneys are the primary organs for drug excretion, with processes including:
  • Glomerular filtration (moves unbound drugs to urine).
  • Passive reabsorption (lipid-soluble drugs re-enter blood).
  • Active transport (involves tubular pumps for organic compounds).

Pharmacodynamics

• Key to ensuring effective medication education, clinical decision-making, and drug effect evaluation.
• Binding with receptors allows drugs to mimic or block actions of endogenous compounds.
• Drugs do not impart new cellular functions, rather they modify existing processes.

Dose-Response Relationship

• Illustrates the relationship between the administered dose and the resultant intensity of response.
• Dose response curve phases:
  • Phase 1: Low doses, minimal response.
  • Phase 2: Dose increments lead to increased responses.
  • Phase 3: Further dose increments yield no additional response.

Drug Receptor Interaction Theories

• Single Occupancy Theory: Response intensity correlates with the number of occupied receptors.
• Modified Occupancy Theory: Multiple drugs can occupy the same receptor, producing varying effects.

Administration and Safety

• Adherence to the "10 rights" of medication administration ensures safety:
  • Right patient
  • Right drug
  • Right dose
  • Right route
  • Right rate
  • Right time
  • Right evaluation
  • Right client education
  • Right documentation
  • Right to refuse
• Monitoring includes checking serum drug levels and liver function tests and may require dose adjustments.

Medication Errors

• Can occur during prescribing, dispensing, or administration stages.
• Common prescription errors include inappropriate drug choice, calculation errors, and therapeutic duplication.

Importance of Client Education

• Proper education enables the patient to understand medication use, effects, and potential side effects, fostering compliance and safety.

This quiz explores key concepts related to allergic reactions, including various types of immunologic responses to drugs. It also covers important drug interactions, focusing on drug-to-drug interactions and their potential effects. Test your knowledge on how allergic reactions can influence medication administration and patient safety.