22B20: Exam Report

Describe the pharmacokinetics of prednisone (50% marks). List the cardiovascular, renal, metabolic, haematological and immunological effects of prednisone (50% marks)

40% of candidates passed this question.

The question asked for detailed information on the pharmacokinetics and selected pharmacodynamics of prednisone.

Most candidates provided unnecessary details of the mechanism of action and pharmaceutics significantly wasting time.

Many provided incorrect information and general information without specifics which is represented by the low pass rate.

The pharmacokinetics part was answered poorly.

It was expected from the candidates to have detailed knowledge on the prednisolone binding capacity and affinity to albumin and corticosteroid binding protein as well as the important metabolism of prednisone.

U2i / 22B20: Describe the pharmacokinetics of prednisone (50% marks). List the cardiovascular, renal, metabolic, haematological and immunological effects of prednisone (50% marks)

Pharmacodynamics of Prednisone

Cardiovascular effects

  • ↑ Number of α1 & β adrenoreceptors →  negative inotropy and vasoconstriction

Renal Effects

  • Na+ retention, K+ excretion

Metabolic Effects

  • Gluconeogenesis
  • Inhibit use of peripheral glucose
  • ↑ Lipolysis
  • ↓ Amino acid protein

Haematological Effects

  • Increased Hb and red cell content of blood (polycythaemia)
  • Increased neutrophil count
  • Altered platelet function
  • Depression of white cell lines due to depression of lymphoid tissue

Immunological Effects

  • Inhibits phospholipase A2 on platelets (normally breaks down phospholipids to give arachidonic acid) → ↓ arachidonic acid → ↓ prostaglandin / leukotriene / interleukin production → ↓ inflammatory response, ↓ oedema, ↓ capillary leakiness, ↓airway responsiveness
  • Blocks neutrophil & macrophage recruitment
  • Blocks lymphokines
  • Inhibits all stages of inflammatory process

Pharmacokinetics of Prednisone

A

  • Rapidly & completely, PO or PR
  • 80 – 100% bioavailability

D

  • PPB 90%
  • VD 0.35 – 0.7L/kg

M

  • Prodrug
  • Metabolised in the liver to the active drug (Prednisolone)
  • This is followed by hydroxylation → conjugation in the liver

E

  • 10% doses unchanged in urine

  • t ½ B 2.5 – 5hrs

Adverse Effects

  • Cushing’s syndrome
  • Acute withdrawal syndrome
  • purpura
  • Peptic ulcer
  • Osteoporosis

Author: Erin Maylin