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.
View full size image. A hypnagogic jerk is an involuntary muscle spasm that occurs as a person is drifting off to sleep. The phenomenon is so named in reference to the hypnogogic state â the transitional period between wakefulness and sleep. Hypnagogic jerks are also commonly known as hypnic jerks or sleep starts. The muscle spasms may occur spontaneously or may be induced by sound, light or other external stimuli.