The effects of enalapril and spironolactone on terbutaline-induced hypokalemia.
OBJECTIVE
To investigate whether enalapril (E) 10 mg and spironolactone (S) 100 mg attenuate the hypokalemic effect of inhaled terbutaline (T).


METHODS
Randomized single-blind crossover. Subjects received the following treatment combinations: (a) placebo (P), (b) T alone, (c) T + E, or (d) T + S.


METHODS
University Department of Clinical Pharmacology.


METHODS
Twenty healthy volunteers (ten male, ten female) of mean age 22.8 +/- 3.1 years.


METHODS
Serum potassium, magnesium, ECG changes (R-R interval, T wave, and QTc interval) for 4 h after terbutaline inhalation.


RESULTS
Baseline serum potassium levels were higher following prior treatment with E and S; P, 3.78 mmol/L (3.67 to 3.88); T + E, 3.93 mmol-1 (3.82 to 4.03); and T + S, 4.03 mmol/L (3.93 to 4.14) (p less than 0.05). Mean potassium concentrations over 4 h were also higher following prior treatment with E and S; T, 3.58 mmol/L (3.54 to 3.63); T + E, 3.68 mmol/L (3.64 to 3.72) (p less than 0.05); and T + S, 3.73 mmol/L (3.68 to 3.78) (p less than 0.01).


CONCLUSIONS
Enalapril and spironolactone protect against the fall in serum potassium over 4 h by elevating baseline potassium concentration. These potassium-sparing drugs, however, should not be used to prevent the hypokalemic and electrocardiographic sequelae of inhaled beta 2-agonists.
Rahman
A R
AR
Department of Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee, Scotland.
McDevitt
D G
DG
Struthers
A D
AD
Lipworth
B J
BJ
D000328:Adult; D004562:Electrocardiography / Q000187:drug effects; D004656:Enalapril / Q000627:therapeutic use*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007008:Hypokalemia / Q000097:blood / Q000139:chemically induced / Q000517:prevention & control*; D008274:Magnesium / Q000097:blood; D008297:Male; D011188:Potassium / Q000097:blood; D012083:Renin / Q000097:blood; D016037:Single-Blind Method; D013148:Spironolactone / Q000627:therapeutic use*; D013726:Terbutaline / Q000037:antagonists & inhibitors*
D013148:Spironolactone; D004656:Enalapril; D012083:Renin; D008274:Magnesium; D013726:Terbutaline; D011188:Potassium