October 1st, 2009
Penicillin allergy is by far the most commonly reported drug allergy. However, the vast majority of patients reporting a penicillin allergy cannot remember ever having had a reaction. Most were told at some point, usually by a parent or grandparent, that they had a penicillin allergy and some even tell me that it simply appeared in their medical chart for unclear reasons. A study once showed that in 20% of hospital admissions, the patient reported an penicillin allergy, but when these people were tested, only 10% of those reporting an allergy were actually positive. So, 90% of people who thought they had a penicillin allergy didn’t!
In penicillin allergy, people can react to different parts of the penicillin molecule. These parts were named major determinants and minor determinants based on the frequency of reactions to the different parts. In the past, testing to the major determinant was done using a commercially available product called Pre-Pen. Unfortunately, Pre-Pen was taken off the market several years ago, leaving allergists with little to test with.
It was announced today the Pre-Pen is coming back. Production is to begin this month, in fact. The product information sheet states that a negative skin test with Pre-Pen gives a less that 5% chance of reacting to therapeutic penicillin.
Our office will be stocking Pre-Pen and performing skin tests and oral challenges in appropriate patients. If you would like to find out if you are really penicillin allergic, let us know.
Dr. O
September 24th, 2009
Currently, influenza vaccines come in two flavors: nasal and injectable. The nasal vaccine is a live, attenuated vaccine. This means that the virus, while still “alive”, has had its cellular machinery crippled so that it won’t cause a whole body infection. The injectable vaccine is inactivated, or killed. It is wholly incapable of causing infection.
The nasal vaccine is very popular in our office. I guess people get enough shots around here, already. Based on a study which came out today in the NEJM, I may be rethinking how I recommend different vaccines.
This study looked at healthy volunteers aged 18 to 49 years. A very important point is that none of these individuals had a condition for which vaccine was explicitly recommended, i.e. healthcare workers, asthmatics, very old, very young, etc. In this study population, the inactivated, injectable vaccine was clearly better at preventing influenza. It wasn’t even close. Rates of infection were 3.5% for the injectable vaccine, 7% for the nasal vaccine, and 11% for placebo.
This study is important in answering which vaccine young, healthy individuals should receive. Results from other studies looking at outcomes in asthmatics have suggested that the nasal vaccine may actually be more effective at preventing influenza related exacerbations. Clearly, this is an important question that needs more data to make a definitive answer.
I got my flu shot BTW
Dr. O
September 16th, 2009
Did you know that elite swimmers have a higher prevalence of asthma than other athletes? Surprisingly, this fact was only confirmed in a study relatively recently. Chlorine was an obvious candidate to explain this finding and over the last decade, evidence has been mounting to suggest that water chlorination does indeed lead to an increased risk of developing not only asthma, but allergies as well.
Initially, the problem was blamed on trichloramine, the gas that gives indoor pools their characteristic smell. Once it was discovered that outdoor pool exposure was as bad as indoor pool exposure, then the focus shifted to chlorine products in the water or vapors present around the water surface.
A recent study from Belgium published in the journal Pediatrics looked at three groups of adolescents, two of which had utilized only chlorinated pools and one of which utilized a pool decontaminated by means of a copper/silver ionizer. I read the study in detail and it is very complicated and has some potential holes. Nevertheless, I think it does clearly demonstrate that kids who spend a large amount of time in a chlorinated pool are more likely to develop asthma and/or respiratory symptoms of cough and shortness of breath and are more likely to develop allergies.
Given that there are other means of decontaminating pools such as salt water or ionizers, regulatory bodies should reconsider the appropriateness of chlorine as the standard pool decontaminant.
Dr. O
September 15th, 2009
Everybody Panic!
This is one of those stories that sounds scary as heck, but really isn’t telling us anything of consequence. If you haven’t heard, some researchers cultured material from showerheads and found high levels of the atypical bacteria Mycobacterium avium intracellulare, or MAI, living there. This isn’t very shocking as MAI is a water loving organism.
Anyway the important point here is that MAI is not very pathogenic. Even if you’re exposed to it, the likelihood of it causing clinical disease is exceedingly low. If you have a very weakened immune system, like late stage HIV or post-chemotherapy, you might take notice, but for the vast majority of us this is a non-issue.
Dr. O
August 17th, 2009
So your feet can affect your lungs?
This is actually an old notion and data continue to gather to suggest that it may be true. The thought process is that molds grow under the toenails and the body develops an allergy to them The same mold may colonize the airways and the allergy response there leads to asthma. We see the same process in the well recognized diseases Allergic Bronchopulmonary Aspergillosis and Allergic Bronchopulmonary Mycosis.
The fungus that grows under the toenails is called trichophyton (try-co-FY-ton). A recent study from Japan published in the Journal, Chest, showed that asthmatics with allergy to trichophyton were much more likely to have severe disease than asthmatics without trichophyton sensitivity. Older studies have suggested that severe asthmatics with trichophyton sensitivity derive benefit from antifungal treatment.
If you have asthma that is not responding to the usual treatment, it may be time to take a look at your feet.
Dr. O
August 13th, 2009
Many of my patients wonder whether preservatives are playing a role in their allergies, particularly hives. This was a hot topic in the allergy world in the 80’s and early 90’s. The most commonly implicated preservative was sodium metabisulfite, which is found in a wide variety of foods. Because it is so common, it became a target for unexplained, chronic hives. When it was studied using blinded, placebo-controlled oral challenges, very few true reactions were observed. Both Dr. Norvell and I trained at Vanderbilt where we had the occasion to supervise many such challenges. Since many people remain concerned about reactions to metabisulfite and other preservatives, at the AAAMT we canperform blinded, placebo-controlled oral challenges if the situation warrants. This remains the gold standard way to evaluate for the presence of preservative, and other, allergies.
July 31st, 2009
The CDC has released its recommendations for the forthcoming swine flu vaccine. The vaccine should be available starting in October and the CDC is suggesting prioritizing whom should receive the first doses, since it may take some time to provide enough vaccine for all. Recommended groups are: (from the CDC website):
- Pregnant women because they are at higher risk of complications and can potentially provide protection to infants who cannot be vaccinated;
- Household contacts and caregivers for children younger than 6 months of age because younger infants are at higher risk of influenza-related complications and cannot be vaccinated. Vaccination of those in close contact with infants less than 6 months old might help protect infants by “cocooning” them from the virus;
- Healthcare and emergency medical services personnel because infections among healthcare workers have been reported and this can be a potential source of infection for vulnerable patients. Also, increased absenteeism in this population could reduce healthcare system capacity;
- All people from 6 months through 24 years of age
- Children from 6 months through 18 years of age because we have seen many cases of novel H1N1 influenza in children and they are in close contact with each other in school and day care settings, which increases the likelihood of disease spread, and
- Young adults 19 through 24 years of age because we have seen many cases of novel H1N1 influenza in these healthy young adults and they often live, work, and study in close proximity, and they are a frequently mobile population; and,
- Persons aged 25 through 64 years who have health conditions associated with higher risk of medical complications from influenza.
You’ll note that one of the usually recommended group, persons aged 65 and older, has been left off the list. It appears that this age group is having fewer problems with the current swine flu strain. Perhaps their immune systems have seen a similar strain in the past.
Dr. O
July 30th, 2009
My last post before leaving for Africa dealt with Xolair and the allergic response. In it I mentioned that there are some risks associated with Xolair use. While I was away, the FDA issued a safety warning on Xolair based on review of a post marketing study. Rather than paraphrase, I’ll just copy their statement:
“The interim data, submitted by the manufacturer of Xolair (Genentech), suggest a disproportionate increase in ischemic heart disease, arrhythmias, cardiomyopathy and cardiac failure, pulmonary hypertension, cerebrovascular disorders, and embolic, thrombotic and thrombophlebitic events in patients treated with Xolair compared to the control group of patients not given the drug…….
FDA is not recommending any changes to the prescribing information for Xolair and is not advising patients to stop taking Xolair at this time. Until the evaluation of the EXCELS study is completed, healthcare providers and patients should be aware of the risks and benefits described in the prescribing information, as well as the new information from the ongoing EXCELS study that may suggest a risk of cardiovascular and cerebrovascular adverse events.
This early communication is in keeping with FDA’s commitment to inform the public about ongoing safety reviews of drugs. FDA has not made any conclusions regarding these data.”
So there you have it. A possibility of an additional risk factor for Xolair without mention of risk percentage or types of events. Even though they’re not sure it’s real, they’re letting us know to keep a close eye on this in the near future.
Dr. O
July 29th, 2009
Jambo. I’m finally back, both physically and mentally, from my three week break. I was with the family on safari in Kenya and Tanzania. It was an amazing experience. Travel really is one of the best teachers.
Needless to say, there’s been some catch-up at work. I’ll be back to posting soon once I can get everything squared away.
Dr. O
July 2nd, 2009
In my last post, I touched on improvements in treating the severest pediatric asthmatics. One thing I noticed in reviewing the info for the post was that 10% of the current study patients were on a medication called Xolair. Xolair, or omalizumab, is a new class of medication that blocks the acute allergic response from occurring. It is only indicated for use in a very few people: severe asthmatics with allergies and an elevated IgE level. This is a little complicated, so some background is helpful.
How Xolair works, image courtesy of NEJM
IgE is an antibody. Antibodies are proteins the immune system makes to help fight off infections. There are three other main antibodies besides IgE: IgG, IgA, and IgM. IgE is the allergy antibody. In the cartoon above, it is represented by the blue Y-shaped figures. One end of IgE binds to allergens like ragweed pollen or cat dander and the other end binds to cells like the mast cell;. When two IgE molecules bound to a mast cell also bind to the same allergen they crosslink. Crosslinking is the signals the mast cell to go to work, which it does by essentially exploding and releasing all kinds of nasty chemicals that make you sneeze, wheeze, and get hives.
Omalizumab is a hybridized, murine, monoclonal antibody directed at the Fc portion of human IgE. Got it? In English, that means that omalizumab, the red Y-shape, latches on to the end of IgE that normally touches the mast cell and prevents it from binding to the mast cell. If IgE can’t bind to the mast cell, then it can’t crosslink and the mast cell is effectively neutralized. It’s like taking the bullets out of a gun.
Studies looking at omalizumab use in severe asthmatics have shown reduction in medication use, improvement in symptoms, and improvement in quality of life. In my own experience, the response has been black-and-white. Some people have made remarkable improvements on omalizumab and some haven’t responded much at all.
Omalizumab is not a cure-all. It is an injectable medication that has to given every 2-4 weeks. There are some risks associated with its use as well. Mostly, it’s incredibly expensive. A 2007 study gives an average monthly cost of $1300. I’m conservative about recommending it to people and in the coming healthcare environment, I’m not sure what its fate will be. That being said, in people with frequent severe exacerbations, ED visits, and/or hospitalizations as well as those on continuous or near continuous oral corticosteroids for asthma, omalizumab can make a huge difference. If you’re a severe asthmatic, ask your doctor about omalizumab/Xolair.
Dr. O
