Monday, June 8, 2020

Why the management of hives and itching in chronic hives (urticaria) may require a higher dose of medications

Disclaimer: Following is not medical advice, please discuss with your physician before making any medical decisions. In the preceding section, we discussed the chemicals released by immune cells that cause effects leading to wheals and itching. Management of hives thus depends on systematically blocking these chemicals released so that they cannot do what they are designed to do. So, 

Due to the predominant role of locally produced histamine, it is clear why antihistamines play such a central role in management of hives. In fact, experts treating chronic hives often recommend daily antihistamines such as cetirizine (e.g. Zyrtec or its generic equivalents), Fexofenadine (e.g. Allegra or its generic equivalents), or Loratidine (e.g. Claritin or its generic equivalent) sometimes in double, triple or even quadruple doses! What would the reason be for this? It comes down to the fact that to cause its mayhem, histamine has to bind to its receptor on cells. Histamine binds to its receptor in a reversible manner, so when an antihistamine comes along, it kicks off the histamine from the receptor and occupies the same place on the receptor site, thus preventing histamine from doing its thing.

Why antihistamines in high doses are often suggested in management of hives

If high dose histamine-1 receptor blockers are not enough, then physicians will often recommend a Histamine-2 receptor blocker. Once the histamine receptor -1 is bound and out of commission, and a person is still having problems with hives, then the next target is to block the histamine 2 receptor. This property belongs to a class of medications, whose most famous role is to suppress acid in stomach. Yep, Ranitidine (Zantac etc, withdrawn from market in 2020) and Famotidine (Pepcid etc) are sold over the counter as acid reflux medications for heart burn. Interestingly, they achieve this by blocking the histamine-2 receptor on stomach lining which reduced acid being produced.

If a person is still breaking out in hives in spite of being on high dose H1 blocking medications, then the next step is to target the Leukotrienes that are also thought to be involved in some patients. This is achieved by a prescription medication called Singulair or Montelukast. This drug blocks the leukotrienes from binding to its receptors and thus blocking their action.

A representation of the ways in which these drugs can help control itching and hiving is given in figure below.

Why the management of hives involves medications such as anti-histamines, acid-reducing medications and Montelukast

Thus you can appreciate that the key to managing the terrible symptoms of chronic hives are sequential and systematic blockade of the pathways involved in the genesis of hives. In fact, the options do not end with the above drug, depending how severe the hives are the options can extend further down the list as noted in the figure below with the last choices being some harsh medications with fair amount of side effects such as immuno-modulators and immuno-suppressants. The last two are almost like 'weak chemo' type medications that are needed to regulate or suppress the immune system, so as to not keep producing those inflammatory chemicals we spoke about earlier.

The inverted triangle of medication choices for hives: More patient can be controlled with the earlier steps and fewer and fewer patient require the progression steps
Hopefully, this article has made clear why the medications in chronic hives are the to be tried the way they are.

To jump directly to other sections in this topic
  1. Why do I get hives all the time with seemingly no cause?
  2. What if my hives bruise, blister, scar or heal with marks on skin?
  3. What is happening in skin that leads to chronic hives? 
  4. What are lifestyle recommendations in management of chronic hives?

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