Thursday, May 1, 2014

What are the common drugs used to treat Mast Cell Activation Disorders?

The majority of the drugs used to control Mast Cell Activation Disorder and Mastocytosis are commonly known.  There is currently no cure for these diseases so it is important to note that these drugs only control symptoms to make life more manageable.

The first class of drugs are referred to as H1 blockers.  These are the conventional antihistamine drugs that many people take for seasonal allergies: Zyrtec/Cetirizne, Claritin/Loratadine, Atarax/Hydroxyzine, Allegra/Fexofenodine and Benadryl/Diphenhydramine. They generally diminish the physical symptoms of itchiness, runny nose, headaches and hives.

Another set of drugs block the H2 receptors found in the digestive track.  Some of those drugs are Zantac/Rantidine, Axid/Nizatdine, Pepcid/Famotidine and Tagamet/Cimetidine. They diminish the amount of acid that is released in the stomach and hence help with heartburn and acid reflux.

When the normal H2 antagonists do not work proton pump inhibitors like Priolosec/Ompreazole, Prevacid/Lansoprazole, Dexilant/Dexalansoprazole, Nexium/Esomeprazole, Protonix/Pantoprazole, and Aciphex/Rebeprazole and used.

People with Mast Cell Activation Disorder or Mastocytosis generally take at least double the normal amount of H1 and H2 drugs or will take multiple drugs of the same class in a given day. Taking the normal doses generally is not helpful since there is such an excess of histamine present.

There are not currently any routinely recommended medications for the H3 receptor located in the brain or the H4 receptor located in bone marrow.  These receptors are not even well understood at this point in time.  Many people are currently researching these receptors and working on finding appropriate antagonists/blockers.

It is important to note that mast cells do not simply release histamine.  Mast cells also release serine proteases like tryptase, serotonin, and preoglycans (mostly heparin).  They also release newly formed lipid mediators like thromboxane, prostaglandin D2, leukotriene C4, and platelet-activating factor.  Finally they also release the cytokine eosinophil chemotatic factor.

Is it clear now why Mast Cell Activation Disorder and Mastocytosis have a widely varying, complex presentation?

Since so many biologically active compounds are released when a mast cell is activated, there are many additional drugs used to control the related symptoms.  I'll elucidate some of the drugs that act against those compounds and the symptoms they diminish in a future post.

If you want to know some of the recommended drugs beyond what I have briefly covered here right now, check out this page from The Mastocytosis Society Canada.