Why aren't antibiotic inhalers commonplace for chest infections?

HarryD

...instead of taking em orally.

I suspect they don't work well, but does anyone know why?

- Less of the common side-effects, experienced with oral antibiotics.
- More direct action against the infection.


TIA,
HD

Dr Galen

admittedly it wouldn't be something I'd see myself as familiar with but I've not seen this in use at all. I remember ages and ages ago something about this type of thing and work being done with CF but that is all I can remember.

SomeDose

It's a good question. I've honestly no idea about trials or studies into inhaled antibiotics but, taking an educated guess, I suspect the reasons that we don't really see this method of administration are:

1) Most current antibiotics used to treat most chest/lung infections can, when administered either orally or IV, achieve a sufficient local MIC to be effective without causing serious adverse effects.

2) Formulation of the drug and achieving acceptable stability would be a pain in the arse. And probably very expensive (Nebulised Tobramycin is mega-expensive).

In some cases they are indeed delivered by inhalation - the most common scenario being chronic lung infections by certain bacteria in cystic fibrosis. Nebulised Tobramycin and Colistin are 2 examples, and are given by this method for essentially the 2 reasons you outlined above. Systemic administration of these at the concentrations required to be effective against the lung bacteria would be quite toxic (especially Colistin), so inhalation allows a relatively high concentration of drug to be delivered directly to the infected site with less risk of systemic toxicity.

For certain swine flu patients, such as those with kidney failure and pregnant women, an inhaled anti-viral is used (Zanamivir/Relenza). Like the examples above, inhalation allows the drug to be delivered locally without risking systemic accumulation to affect the patient's kidneys or harm the foetus.

Other antimicrobials are given in rare instances by inhalation for certain infections, but these are usually unlicensed methods of putting an IV solution through a nebuliser.

DrIndy

if you think about it logically - you need to get the antibiotics into the site where the bugs are. If you inhale antibiotics - they will work on the site where they get to - the airways.

However, a pneumonia is a consolidation where the lung tissue fills with bacteria and infection fighting cells - there is very little or no air entry into this tissue mass so inhaled antibiotics would not get to the site of infection.

Likewise a predominant bronchitis has infection fighting cells coating the airways targetting the bacteria (aka - phlegm) This coating would prevent an inhaled antibiotic getting deep to the location of the bacteria.

This is why you treat with IV or oral antibiotics - the blood vessels conduct it to the right place.

The place for inhaled or nebulised antibiotics is in fact to PREVENT infection. In chronic colonised people because of lung scarring, normal protective mechanisms are gone and so bacteria can persist hiding in these spaces - there is no associated phlegm etc... as there is no active infection. Here the nebulised antibiotics suppress the bugs but are less useful during an true exacerbation of infection as once again, they are coated off by phlegm and neutrophils.

In normal people, they do no good - you do not have any dead spaces for bugs to hide as the normal protective mechanisms are in full swing.

Hence its all oral or IV treatment.

The equivalent thing is to rub an antiseptic ointment on a skin abscess - it won't do anything at all.

SomeDose

DrIndy wrote: »

The place for inhaled or nebulised antibiotics is in fact to PREVENT infection. In chronic colonised people because of lung scarring, normal protective mechanisms are gone and so bacteria can persist hiding in these spaces - there is no associated phlegm etc... as there is no active infection. Here the nebulised antibiotics suppress the bugs but are less useful during an true exacerbation of infection as once again, they are coated off by phlegm and neutrophils.

True - I should've added that things like nebulised tobramycin are most effective for reducing exacerbations and severe acute infections in chronically colonised CF patients. However, and this is where my lack of knowledge of CF airways pathology might let me down, would these patients not already have increased amounts and viscosity of sputum / mucus in their airways anyway? In other words, it should still have local anti-pseudomonal activity despite these barriers. I think variations in pathology and nebuliser technology also probably account for differences in bactericidal activity.

I think there's also a few isolated studies of using nebulised antibiotics aseffective adjuncts to IV therapy in severe ITU / VAP-type respiratory infections.

tallaght01

We use nebulised tobra in a lot of our CF kids, but like DrIndy says, once you've got consolidation, you've gotta go IV. You will get droplet dissemination in mucous easier than you will in a consolidated lobe, where you can hardly get any air in.

DrIndy

SomeDose wrote: »

True - I should've added that things like nebulised tobramycin are most effective for reducing exacerbations and severe acute infections in chronically colonised CF patients. However, and this is where my lack of knowledge of CF airways pathology might let me down, would these patients not already have increased amounts and viscosity of sputum / mucus in their airways anyway? In other words, it should still have local anti-pseudomonal activity despite these barriers. I think variations in pathology and nebuliser technology also probably account for differences in bactericidal activity.

I think there's also a few isolated studies of using nebulised antibiotics aseffective adjuncts to IV therapy in severe ITU / VAP-type respiratory infections.

I think you have hit the nail on the head as adjunctive treatment.

In Cystic Fibrosis and Bronchiectasis - there is dead space in the lungs from scarring which has no blood supply and no normal mucosal function and thus is a repository for bugs to hide - nebulised antibiotics do get in to suppress but also would help IV therapy (which is targetting areas of active infection) by dealing with the bits that the blood supply misses.

HarryD

Thanks all