Expert: William J. Walker, Pharm.D. - 6/4/2004

Question
Hello.  Re: the two medications in the combivnet inhaler:  can you briefly explain  the two types of meds in the inhaler and what each one is suppose to do?  ( one is suppose to help shortness of breath)  Thank you!

Answer
Actually both components of Combivent are to help prevent shortness of breath.    They work together,   in tandem,   by two separate pathways.

One of the agents is albuterol.   Perhaps the most common and widely used beta agonist.    It is a medication that stimulates the beta-2 receptors which are located primarily in the lung tissue.    These are part of the sympathetic nervous system where neurohormonal control of various bodily functions are managed by several substances released by neurons.    Adrenalin being the most common.     Albuterol is a compound that seems to mimic this activity only at beta 2 receptors meaning that it has little to no activity on cardiovascular tissues.   This is why it is so useful as it has a low potential to illicit annoying sympathetic cardiac side effects such as tachycardia or hypertension.    What it does though is directly cause bronchodilation.    This increases the surface area of the oxygen exchange absorptive tissue and allows for more oxygenation to take place.    The net result is improved breathing.

The other agent is ipratropium also known as Atrovent.    Ipratropium is a substance that impacts the parasympathetic nervous system.    Similar to what I described already there is an opposing nervous system that operates in a balance.    Using acetylcholine as the primary neurotransmitter there are many functions governed by this system usually in the reverse or opposite direction.    So that in stimulating this system one would expect aggravation of shortness of breath.    Ipratropium functions as a cholinergic blocker as it works to prevent the cholinergic action at receptors.    Normally these anticholinergic medications are far too potent with other side effects to be of any value.     Causing dry mouth,   tachycardia,   constipation,   and blurred vision.   Too harsh to warrant benefit.    Ipratropium is one agent that acts locally only without resulting in these other side effects.    So that delivery into the lungs provides the value of bronchodilation without other side effects.    Using these two agents together can increase the outcome at lower dosages by using two separate pathways.     One could use two separate inhalers,   as is the method used before Combivent,   or simplify things with one inhaler.    

The downside of this product is that it is a fixed dosage and not allowing for flexibility.    And it requires four doses per day compared to some other approaches requiring less.