Sorry to drag up an old thread but in case anyone was still wondering about the safety of guaif in their ephedrine:
From a March 2009 article in the journal Current Allergy and Asthma Reports:
Guaifenesin (glyceryl guaiacolate) is a mucoactive
agent that has been successfully marketed in the United
States for more than 50 years in a variety of over-thecounter
cough and cold medicines [6]. It is classifi ed as
an expectorant rather than a mucolytic agent based on its
ability to reduce mucus viscosity while increasing sputum
volume, thereby promoting more effective coughing and
expectoration [1,6,7,8•]. Guaifenesin is the only expectorant
considered effective by the US Food and Drug
Administration [9]. The recommended doses range from
400 to 1200 mg/d, but doses up to 2400 mg/d may be
needed for some patients [7].
Mucus is a complex mixture of water, lipids, mucus
glycoproteins, sugars, proteins, and electrolytes. It serves
three roles—as a protectant, a barrier, and a first level of
host defense. The human body
manufactures about 2 quarts of respiratory mucus per
day, which is usually swallowed unconsciously.
from RxList:
Guaifenesin is well tolerated and has a wide margin of safety. Side effects have been generally mild and infrequent. Nausea and vomiting are the side effects that occur most commonly. Dizziness, headache, and rash (including urticaria) have been reported rarely.
The acute toxicity of guaifenesin is low and over-dosage is unlikely to produce serious toxic effects. In laboratory animals no toxicity resulted when guaifenesin was administered by stomach tube in doses up to 5 grams/kg.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Animal studies to assess the long-term carcinogenic and mutagenic potential or the effect on fertility in animals or humans have not been performed.
So it looks pretty safe- but I'm not going to take it every day for my whole life, either.