Possible side effects of Alka-Seltzer effervescent tablets: All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome: Heartburn; nausea; upset stomach.
A myoclonic jerk is the brief, involuntary twitching of a muscle or group of muscles. It may be caused either by a sudden muscle contraction, or a sudden lapse of contraction.
Myoclonic seizures. Most people have experienced an abrupt jerk as they are falling asleep (normal sleep myoclonus) or have jumped when someone gives them a fright and this is similar to the jerk experienced by a child who has a myoclonic seizure. Myoclonic seizures are like being jolted by a mild electric shock.