Member's Mark Arthritis Pain Acetaminophen 650 mg is used for the temporary relief of minor pain caused by arthritis, backache, toothache, headache, muscular aches, and the common cold. Members Mark Arthritis Pain Acetaminophen also temporarily reduces fever. The active ingredient in each caplet is Acetaminophen USP, 650 mg. Members Mark Arthritis Acetaminophen Extended-Release caplets compares to Tylenol Arthritis 8-hour pain active ingredient and contains two 200 count bottles.