I'm on medication for GERD and reflux treatment ie nexium, (esomeprazole) ganaton & duspatalin. However I been getting muscle cramp every now and then, why is that?

Hypomagnesemia. Some people get problems with magnesium absorption in small bowel or you may be on diuretics or have malabsorption--so you could measure magnesium in blood or just get magnesium supplements from over the counter- 1-muscle cramps has a variety of other causes?Get blood work-- 2- try to go without Nexium (esomeprazole) and see if muscle cramps go away.