Lithium + Diuretics; Potassium-sparing - Drug Interactions

There is evidence that excretion of lithium can be increased bytriamterene. In contrast,serum-lithium levels may rise ifspironolactone is used. Amiloride appears not to interact. See alsoLithium + Diuretics; Loop interaction,above, and Lithium + Diuretics;Thiazide and related, p. 1123.

Amiloride has been found to have no significant effect on serum-lithium levels when used in treatment of lithium-induced polyuria (See reference number 1,2). One review briefly mentions a case report in which amiloride was successfully used as a replacement for bendroflumethiazide,which had caused lithium toxicity (See reference number 3). However, some manufacturers(See reference number 4,5) suggest that, as a diuretic, amiloride reduces renal clearance of lithium, thereby increasing risk of lithium toxicity. There appears to be no evidence to confirm this alleged interaction.

One study found that spironolactone had no statistically significant effect on excretion of lithium (See reference number 6). Whereas, in another report, use of spironolactone 100mg daily was accompanied by a rise in serum-lithium levels from 0.63 to 0.9 mmol/L. The levels continued to rise for several days after spironolactone was stopped (See reference number 7).

Triamterene,given to a patient taking lithium while on a salt-restricted diet, is said to have led to a strong lithium diuresis (See reference number 8). Similarly,triamterene increased lithium excretion in 8 healthy subjects (See reference number 9).

These diuretics have been available for a very considerable time and it might have been expected that by now any serious adverse interactions with lithium would have emerged,but information is very sparse. None of reports available gives a clear indication of outcome of concurrent use, but some monitoring would be a prudent precaution. Patients on lithium should be aware of symptoms of lithium toxicity (see Lithium, ) and told to report them immediately should they occur.

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