The Decision Tree casually describes loratadine (brand name: Claritin) as barely better than placebo for treating allergies. This is news to me because Claritin was absolutely critical to me graduating middle school. If I forgot to take it in the morning my mom had to drop it off at school by lunch. Without it I slept 16 hours a day,* woken up only by hives that itched so intensely they burned. This isn’t actually relevant to me now because my allergies were taken care of my unprocessed honey and moving, but I couldn’t believe something once so important was essentially a sugar pill. So I investigated.
First stop, Wikipedia, which definitely backed my claim that Claritin treated sneezing, runny nose, itchy or burning eyes, hives, and other skin allergies. But of 19 citations, 5 were unavailable to me (either they were books or in languages I don’t read), 13 were on topics other than clinical efficacy (e.g. side effects or mechanism), and 1 had a sample size of 192 and was a comparison against another anti-histamine, with no placebo or no-treatment group.
So I checked google scholar, where I found numerous minuscule studies (n = 14, 7 treatment groups) in which loratadine was better than placebo but worse than other drugs in the same class.** If that’s true, why did loratadine get so much more attention? I looked up the other drugs, and it turns out that some of them (cetirizine/Zyrtec) had similar efficacy but came out later, and went over the counter later as well. Others (Terfenadine/Seldane) had much uglier side effect profiles (e.g. cardiac arrythmia if you eat a grapefruit). So Claritin’s advantage seems to be being the first drug to market that treated the problem with minimal side effects. I also wonder if Decision Tree‘s author (Thomas Goetz) was looking at a particular symptom set? For example, loratadine appears to do well as a treatment for hives but there are better options for hay fever.
Some people suggest that having multiple drugs with similar response rates in the same class on the market is some sort of failure. They are wrong and they should feel wrong. First, these drugs were developed in parallel by different companies. While all the ones we heard of worked out, very few chemicals that pharma companies research become prescribable drugs, and they can’t predict which ones will do so ahead of time. What if McNeil stopped researching Zyrtec because Bayer was researching Claritin, and Claritin made you grow arms out of your face? We’d have lost years of allergy relief. Second, the fact that they had similar average efficacy and side effects doesn’t mean they have the same effect in every person. People are squishy and they don’t make sense, and differing reactions to drugs is one of the milder ways this manifests.
*No, fatigue is not a normal symptom of allergies, but I got it most springs and it went away with anti-histamines, which is good enough for a field diagnosis of allergies.
**I also found a lot of studies detailing the effects of loratadine in conjunction with another drug, mostly montelukast, and abstracts that reported loratadine’s efficacy relative to older antihistamines but without absolute numbers.