When I first started my mestinon, I got the rippling muscle sensation, the muscles twitch repeatedly on there own, I had it in my back, rib cage area, arms & legs, around my mouth. The doctor told me it was the mestinon, & it happens sometimes with the weakened muscles & your body getting used to the dosage. If you, start having trouble swallowing, & breathing, or extreme weakness, call 911, don't wait !