Influence of combined angiotensin-converting enzyme inhibitors and spironolactone on serum K+, Mg 2+, and Na+ concentrations in small dogs with degenerative mitral valve disease.

OBJECTIVE

To determine if the administration of an angiotensin-converting enzyme inhibitor (ACEI) plus spironolactone caused hyperkalemia, hypermagnesemia, or hyponatremia in elderly small dogs with degenerative mitral valve disease (MVD).

BACKGROUND

ACEIs and spironolactone can increase serum potassium and magnesium concentrations and lower serum sodium concentrations. It has been recommended to either not combine these drugs or to do so with caution. ANIMALS, MATERIAL AND METHODS: Fifty client-owned dogs with MVD, left atrial dilation, and without congestive heart failure or azotemia were evaluated retrospectively. Baseline data sets, followed by 1-9 (mean=2.66) data sets, comprised of serum urea nitrogen (SUN), creatinine, sodium, potassium, and magnesium concentrations, were tabulated. Each dog received an ACEI plus spironolactone for a mean of 23.8+/-26.6 weeks (range: 2-150) and a median of 15 weeks. No cardiac drugs other than an ACEI and spironolactone were administered during the study period.

RESULTS

There were no significant differences between baseline and follow-up serum sodium or potassium concentrations. Serum magnesium concentrations increased significantly (p=0.02) with time >20 weeks compared to baseline.

CONCLUSIONS

The combination of an ACEI and spironolactone results in no significant difference between baseline and follow-up serum sodium or potassium concentrations. Although serum magnesium concentrations may increase significantly with time >20 weeks compared to baseline concentrations, hypermagnesemia appears to be rare, mild, and unlikely to be of clinical importance. The combination of an ACEI and spironolactone is safe in elderly small dogs with MVD with normal SUN and creatinine concentrations.