Lithium xanthines

Acetazolamide, alkalizing agents, xanthine preparations, and urea may lower lithium plasma concentrations... 

Lithium is also known to interact in a variety of ways with different classes of diuretic drugs. Thiazide diuretics increase serum lithium concentration by increasing reabsorption of lithium, along with that of sodium, in the proximal tubule. With potassium-sparing diuretics, conflicting results have been reported. Increased serum lithium concentrations may be seen after amiloride. However, the loop diuretic furosemide safely can be combined with lithium with no reduction in renal lithium clearance or consequent increase in serum lithium concentration (191, 192). Other diuretics, for example, carbonic anhydrase inhibitor and xanthine derivatives, decrease serum... 

Other xanthines e.g. caffeine appear to have a similar effect, see Lithium + Caffeine , p.ll20. 

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