Wash. Rev. Code § 69.04.420
If a drug or device purports to be or is represented as a drug the name of which is recognized in an official compendium, and its strength differs from, or its quality or purity falls below, the standard set forth in such compendium, it shall be deemed to be adulterated. Such determination as to strength, quality or purity shall be made in accordance with the tests or methods of assay set forth in such compendium or prescribed by regulations promulgated under section 501(b) of the federal act. No drug defined in an official compendium shall be deemed to be adulterated under this section because it differs from the standard of strength, quality, or purity therefor set forth in such compendium, if its difference in strength, quality, or purity from such standard is plainly stated on its label. Whenever a drug is recognized in both the United States pharmacopoeia and the homeopathic pharmacopoeia of the United States, it shall be subject to the requirements of the United States pharmacopoeia unless it is labeled and offered for sale as a homeopathic drug, in which case it shall be subject to the provisions of the homeopathic pharmacopoeia of the United States and not to those of the United States pharmacopoeia.
RCW 69.04.420