Carbonic anhydrase inhibitors + ADH antagonists Flashcards
Carbonic anhydrase (CA) inhibitors - 2 drugs + adm
Acetazolamide - oral
Dorzolamide - topical ocular
CA inhibitors - indications
High-altitude sickness.
Glaucoma (chronic and acute).
Alkalinization of urine.
Epilepsi (elevates seizure threshold).
CA inhibitors are usually not used for … because…
Not used for diuresis. They are weak diuretics
Dorzolamide - elimination
Biphasic elimination, second phase caused by slow release from RBCs. 4 months half-life.
Acetazolamide, dorzolamide- MOA
Inhibition of carbonic anhydrase, inhibiting formation of bicarbonate.
Why are the CA inhibitors useful in glaucoma?
Inhibits aqueous humor secretion. CA catalyzes formation of bicarbonate which is a constituent of aqueous humor.
CA inhibitors - effects on kidneys
Inhibits reabsorption of sodium bicarbonate in proximal tubule and secretion of hydrogen in collecting duct.
Alkalinization of urine and mild hyperchloremic metabolic acidosis because of increased chloride reabsorption.
CA inhibitors - adverse effects
Oral adm: drowsiness, paresthesia, hypokalemia, hyperglycemia, hypersensitivity, blood cell deficiencies, hepatic insufficiency, metabolic acidosis, uremia.
Dorzolamide: Bitter taste, blurred vision, ocular discomfort, allergic reactions.
CA inhibitors - interactions
Decrease excretion of weak bases (amphetamine, psuedoephrine, quinidine).
Salicylates increases CA inhibitor levels.
Antidiuretic hormone antagonists - 2 drugs + adm
Tolvaptan - oral
Conivaptan - IV infusion
ADH antagonists - MOA
Conivaptan: blocks V1 and V2 receptors.
Tolvaptan: blocks V2 receptors.
V2 receptor inhibition blocks insertion of aquaporin channels in collecting ducts. Causes free water excretion
ADH antagonists AKA
Aquaretics
Conivaptan, tolvaptan - indications
Euvolemic and hypervolemic hyponatremia in hospital.
ADH antagonists - contraindications
Hypovolemic hyponatremia.
CYP3A4 inhibitors
Aquaretics - interactions
CYP3A4 inhibitors.
Increase levels of midazolam and simvastatin.
