(c) Narcotic drugs containing nonnarcotic active medicinal ingredients. Any compound, mixture, or preparation containing any of the following narcotic drugs, or their salts calculated as the free anhydrous base or alkaloid, in limited quantities as set forth below, which shall include one or more nonnarcotic active medicinal ingredients in sufficient proportion to confer upon the compound, mixture, or preparation valuable medicinal qualities other than those possessed by narcotic drugs alone:

1. (1) Not more than 200 milligrams of codeine per 100 milliliters or per 100 grams.
2. (2) Not more than 100 milligrams of dihydrocodeine per 100 milliliters or per 100 grams.
3. (3) Not more than 100 milligrams of ethylmorphine per 100 milliliters or per 100 grams.
4. (4) Not more than 2.5 milligrams of diphenoxylate and not less than 25 micrograms of atropine sulfate per dosage unit.
5. (5) Not more than 100 milligrams of opium per 100 milliliters or per 100 grams.
6. (6) Not more than 0.5 milligram of difenoxin and not less than 25 micrograms of atropine sulfate per dosage unit.