The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 56

70. What is premedication and when should I do it?

Premedication is taking extra medication in advance of doing something that you expect to trigger your mast cells. The current premedication protocol for mast cell patients is as follows:
Prednisone 50mg orally (20mg for children under 12): 24 hours and 1-2 hours before procedure
• Diphenhydramine 25-50mg orally (12.5 mg for children under 12) OR hydroxyzine 25mg orally, 1 hour before procedure
• Ranitidine 150mg orally (20mg for children under 12) 1 hour before procedure
• Montelukast 10mg orally (5mg for children under 5) 1 hour prior to procedure

This protocol was developed for the Mastocytosis Society by Dr. Mariana Castells and the original can be found here.

This premedication protocol uses medications to interfere with the molecules mast cells release as well as medication to decrease the amount of molecules mast cells make and release. Diphenhydramine (called Benadryl in the US) stops histamine from getting to the H1 histamine receptors on the outsides of many cells. Ranitidine stops histamine from getting to the H2 histamine receptors on the outsides of many cells. In these ways, these medications can help to stop symptoms from histamine released by mast cells.
In a similar way, montelukast stops leukotrienes from getting to receptors on cells. This helps to curb some of the symptoms that occur when leukotrienes are released by mast cells.

Prednisone is a glucocorticoid, commonly called referred to as a “steroid.” This medication suppresses the production and release of inflammatory molecules by mast cells and other immune cells. Importantly, this medication can take hours to achieve maximum effect. This is why the first dose is the day before the event for which you are premedicating. By being dosed again a couple of hours before the event, it can also provide some additional protection for delayed reactions.

It is important to know that this premedication protocol may need to be changed to achieve the most effective protocol for individual patients. These recommendations are general and are not based upon study or clinical trial data.

This procedure is intended to be used for all major and minor medical procedures, including imaging tests like x-rays and MRIs, whether or not they use contrast. However, many patients find some benefit in premedicating for other types of events as well, such as flying, childbirth, and days of planned elevated physical or emotional stress. Patients should discuss what sorts of events are appropriate to premedicate for with a knowledgable provider.

For more detailed reading, please visit the following post:
Premedication and surgical concerns in mast cell patients