It would be hard to know without doing electrolyte testing, and sometimes that doesn't really tell you what's going on in the tissues. But Lasix definitely causes potassium loss and weakness is a sign of that (so is increased nerve pain).

As long as your myotonia isn't really severe it would be worth trying to increase your potassium and see what happens. You can also take a supplement.

I would let your doctor know and see if you can get some testing. This is what the product information says about side effects:

"All patients receiving LASIX therapy should be observed for these signs or symptoms of fluid or electrolyte imbalance (hyponatremia, hypochloremic alkalosis, hypokalemia, hypomagnesemia or hypocalcemia): dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, arrhythmia, or gastrointestinal disturbances such as nausea and vomiting. Increases in blood glucose and alterations in glucose tolerance tests (with abnormalities of the fasting and 2-hour postprandial sugar) have been observed, and rarely, precipitation of diabetes mellitus has been reported."

So definitely ask to be monitored because too little potassium can affect your heart.

Jan

Type of Myotonia: Thomsen\'s

Country: US