Expectorants

	
Guaiphenesin
	
Mechanism of action:
 
As an expectorant, Guaiphenesin is used to promote the expectoration of 
bronchial secretions (AMH, 2004) by decreasing sputum viscosity, and hence 
facilitating its removal It also increases the amount of respiratory tract
fluid thereby having a demulcent action on the mucosal lining. (Merck Manual).

Dicpinigaitis and Galye (2003) proposed that guaiphenesin inhibits the cough 
reflex sensitivity in patients with a URTI, whereby these patients have cough
receptors that are transiently hypersensitive. Inhibition of the cough reflex 
was postulated to have been achieved by guaiphenesin having either a central 
anti-tussive effect or a peripheral effect. If it is indeed the later, then 
Dicpinigaitis and Galye thought that guaiphenesin increased sputum volume as
a barrier to shield the cough receptors within the respiratory epithelium 
from tussive stimulus

Contra-indications:
There has been no evidence to show that Guaiphenesin is contra-indicated in any 
disease state, and subsequently can be used in combination with any drug. 

Disease state information:
All evidence indicates that Guaiphenesin should be only be used for the 
treatment of an acute cough of unknown or URTI cause, and only after all other
possible conditions (asthma, COPD, etc) have been excluded. Parvez et al. (1996),
however, looked at the effects Guaiphenesin had on a chronic cough.

Protocols for the use of Guaiphenesin:
Within the Cochrane Database of Systematic Reviews, Schroeder and Fahey 
(2004) reviewed the use of OTC medications for acute cough in children and 
adults in ambulatory settings. Schroeder and Fahey found that guaiphenesin 
had been included in two trials, both performed in adults only. 

The first trial was performed by Robinson (1977) and was a random controlled 
trial (RCT) with n=239 participants. Each participant was given a dose of either
guaiphenesin 200mg/10ml qid 3/7 or a placebo. Of those patients, 75% 
(79/105) stated that guaiphenesin was helpful after 72hrs in reducing cough 
frequency and intensity compared with 31% (33/106) in the placebo group. The 
outcomes in this study were reported based on a patient questionnaire and a 
cough score of 0-3. The only adverse drug reactions that were reported in this
trial were from 4 participants; 2 receiving guaiphenesin reported nausea and
urticaria, 2 receiving placebo reported headaches, drowsiness and excessive 
perspiration. A conclusion that could be drawn from this study is that 
guaiphenesin is effective in reducing a coughs frequency and intensity.

The second trial was performed by Kuhn (1982) and was also a RCT with n=65 
participants. Unlike Robinson, Kuhn looked at the anti-tussive effect of 
guaiphenesin. Each participant was given a dose of either 480mg/30ml q6h for 
30hrs or a placebo. Of those patients, 100% (33/33) of patients receiving 
guaiphenesin reported improvements after 36hrs in cough frequency and 
severity compared with 94% (30/32) and 91% (29/32) respectively in those 
patients receiving the placebo. 96% of the guaiphenesin users reported reduced
sputum thickness compared with 54% of the placebo users. The outcomes in this
study were reported based on tape recordings of cough frequency as well as a 
patient questionnaire on 6 symptoms. A conclusion that could be drawn from 
this study is that guaiphenesin is not effective in cough frequency and 
intensity, but is effective in reducing sputum thickness.

Schroeder and Fahey concluded that there was no good evidence for or against
the effectiveness of OTC medications in the treatment of an acute cough. This
was possibly due to the limited number of patients involved in each trail.