Question

Theophylline by what mechanism causes diuresis ?

• A. PDE3 inhibition
• B. PDE4 inhibition
• C. Beta 2 agonist action
• D. Adenosine A1 receptor antagonism

Answer 1

The Correct Option is D

Theophylline is a methylxanthine drug that primarily causes diuresis through its action as an adenosine A1 receptor antagonist. Theophylline's mechanism of action in promoting diuresis can be explained as follows:

• Theophylline inhibits the activity of adenosine A1 receptors in the kidneys. Adenosine normally acts on these receptors to promote sodium reabsorption and smooth muscle contraction in the renal vasculature.
• By antagonizing adenosine A1 receptors, theophylline decreases sodium reabsorption in the proximal tubule of the nephron. This reduction in sodium reabsorption decreases water reabsorption, leading to increased urine output or diuresis.
• This mechanism is distinct from phosphodiesterase (PDE) inhibition or beta-2 agonist activities. While theophylline does have effects on PDE inhibition, its diuretic effect is primarily attributed to adenosine receptor antagonism.

Therefore, the correct answer to the question is: Adenosine A1 receptor antagonism.