Table 3 Pharmacology studies

Chodosh (1973)

To evaluate sputum changes associated with guaifenesin in chronic bronchial conditions

Double-blind crossover study:

1 week known placebo +800 mg/day or 2400 mg/day for 4 weeks +1 week unknown placebo +1000 mL extra oral water intake

Significantly uniform and beneficial changes, such as sputum adhesiveness and dry weight, occurred with 2400 mg/day guaifenesin

Thomson (1973)

To assess the effect of guaifenesin on mucociliary clearance (MCC) in the human lung from the rate of removal of inhaled radioactive tracer particles

Double-blind crossover study:

600 mg guaifenesin vs placebo

Significant improvement in mucociliary clearance with guaifenesin in patients with chronic bronchitis but not in healthy subjects

Sisson (1995)

To examine:

(i) The effect of guaifenesin on nasal MCC in vivo (assessed by saccharin transit time [STT]) and nasal ciliary beat frequency (CBF; assessed by nasal brushing and ex vivo microscopy), and

(ii) whether a relationship exists between nasal CBF and nasal STT

Double-blind crossover study:

400 mg guaifenesin vs placebo 5× daily from days 1 to 7, or days 14 to 21

No significant differences between guaifenesin- or placebo-treated groups in change from baseline values of STT or CBF

No relationship observed between STT and CBF from regression analysis

Dicpinigaitis (2003)

To evaluate the effect of guaifenesin on cough reflex sensitivity to inhaled capsaicin in healthy subjects and subjects with acute URTIs

Randomized double-blind study:

Single dose of 400 mg guaifenesin vs placebo

Cough reflex sensitivity was statistically significantly decreased with guaifenesin in patients with URTIs but not in healthy subjects

Dicpinigaitis (2009)

To evaluate the antitussive effect of the combination of benzonatate and guaifenesin in subjects with acute URTI

Randomized double-blind crossover study (n = 23):

Each subject received 3 of 4 possible study drug/combinations:

600 mg guaifenesin (G), 200 mg benzonatate (B), their combination (B + G), and placebo (P)

• Guaifenesin (p = 0.01) significantly inhibited cough reflex sensitivity relative to placebo

• B + G combination suppressed capsaicin-induced cough significantly more than B (p < 0.001) or G (p = 0.008) alone

Bennett (2010)

To determine whether guaifenesin improves MCC in the healthy lung by assessing the rate of removal of inhaled radioactive tracer particles

Open-label randomized crossover study (n = 8):

Single dose of 1200 mg guaifenesin vs placebo over 3 weeks; minimum 7-day washout period

Strong trend toward statistical significance (p = 0.07) for enhanced small airway clearance with guaifenesin vs placebo

Bennett (2015)

To determine the effect of guaifenesin on MCC and cough clearance in non-smoking adults with acute URTI by assessing the rate of removal of inhaled radioactive tracer particles

Randomized double-blind crossover study:

Single dose of 1200 mg guaifenesin vs placebo

No significant effect of single dose guaifenesin on mucociliary and cough clearance compared to placebo