the well-known difficulty in distinguishing the response to a combination headache medication and its individual components in the presence of a high placebo response was again demonstrated in a randomized , double-blind , placebo-controlled , multi-center trial comparing fiorinal with codeine and its fiorinal and codeine phosphate components in relieving the pain , tension , and muscle contraction associated with tension headache .
C0009217
codeine phosphate
C0030193
pain