Inhaled corticosteroids (ICS) have been the mainstay of asthma treatment for over 30 years. The steroid molecules have improved considerably over time, with greater topical potency and less systemic side effects. During that time, numerous studies have shown that ICS are effective at reducing symptoms, exacerbations, hospitalizations, and death due to asthma. Likewise, there have been numerous studies examining the side effects of these medications which have shown that in low to medium doses, there are few if any systemic complications. In the highest doses, there may be a slight increase in cataracts and loss of calcium from the bone. But, and this is a very important point, these risks have to be weighed against the risks of the alternative: more symptoms, more exacerbations and more oral steroid use.
A common concern voiced by patients and parents is, “I don’t like taking medications” or “I don’t want my child to be on daily medications”. It’s right to be thoughtfully critical of regular medication use, but, by the same token, if regular medications are helpful and are the better alternative, then they are a good choice. In order to explain why regular ICS are a good choice, I’ve got to do a little math. Let’s say you were just using a rescue inhaler for asthma control and that during the last year you only required one course of oral steroids, prednisone. A usual prednisone “burst” is 40mg a day for 5 days for a total of 200mg or 200,000mcg. By way of comparison, each dose of Advair 100/50 contains 100mcg of fluticasone, the steroid. If you took Advair 100/50 twice a day, the usual dose, it would take you 1000 days of regular use to equal the amount of steroids in one burst of prednisone on a mcg-per-mcg basis.
But wait, there’s more. When you swallow a predinisone pill, 100% of the drug makes it into your system. Doctors call this bioavailability. In contrast, the bioavailability of inhaled steroids, especially the newer molecules is very low, from 1-6%. Why is this? When you use an ICS, you swallow a significant amount of the drug. When the swallowed portion is absorbed in the stomach, it travels directly to the liver where it is broken down and inactivated. This is called first pass metabolism. A part of the inhaled portion of the drug can still make it into the blood stream. This part is not immediately inactivated by the liver and, therefore, is the portion which can lead to systemic side effects. So, back to the math: if only 1% of the inhaled steroid dose in Advair is bioavailable, then you multiply 1000 days by 100 to get 100,000 days of regular use to equal one burst of prednisone on a bioavailable mcg-per-mcg basis.
To be completely honest, the newer inhaled steroids are more potent than prednisone on a mcg-per-mcg basis which means the 100,000 day number is inflated. Also, the amount of steroid that is absorbed and the subsequent systemic side effects vary based on delivery device, inhaler technique, and timing of administration. Nevertheless, the underlying point holds true: one round of oral steroids is worth a whole lot of inhaled steroids. Given this and the quality of life improvements afforded by regular inhaled steroids, in all but the mildest asthmatics the tradeoff is a no-brainer.