Absorption
Guaifenesin is well absorbed from the gastro-intestinal tract following oral administration, although limited information is available on its pharmacokinetics. After the administration of 600 mg guaifenesin to healthy adult volunteers, the Cmax was approximately 1.4 ug/ml, with tmax occurring approximately 15 minutes after drug administration.
Menthol is well absorbed from the gastrointestinal tract following oral administration.
Distribution
No information is available on the distribution of guaifenesin or menthol in humans.
Metabolism and elimination
Guaifenesin appears to undergo both oxidation and demethylation. Following an oral dose of 600 mg guaifenesin to 3 healthy male volunteers, the t½ was approximately 1 hour and the drug was not detectable in the blood after approximately 8 hours.
Menthol is hydroxylated in the liver by microsomal enzymes to p-methane -3,8 diol. This is then conjugated with glucuronide and excreted both in urine and bile as the glucuronide.
Pharmacokinetics in Renal/Hepatic Impairment
There have been no specific studies of this product, menthol or guaifenesin in hepatic or renal impairment.
Pharmacokinetics in the Elderly
There have been no specific studies in the use of this product, menthol or guaifenesin in the elderly.