Medications to Avoid with MCAS

Updated: Mar 18


Your mast cells are necessary for your body’s health and function. However, overactive mast cells can lead to mast cell disorders, such as mast cell activation syndrome (MCAS). When your mast cells are activated, it leads to the secretion of histamine and other inflammatory mediators. This can cause unwanted symptoms.

Certain medications are among one of the main triggers of MCAS. Understanding what medications you need to avoid with MCAS is critical for managing the condition. Today I want to go over what medications to avoid, if possible. I will also discuss potential problems with “excipients” in MCAS. Let’s get into it.


Symptoms of MCAS Triggered by Medication

MCAS may be triggered by certain medications and excipients which may result in a variety of symptoms. Your symptoms may include, but are not limited to:

  • Fatigue

  • Malaise

  • Weakness

  • Dizziness

  • Digestive troubles

  • Headaches

  • Flushing

  • Anaphylaxis

  • Hives

  • Itchy skin

  • Skin rashes

  • Insomnia

  • Chest pain

  • Vision changes

  • Blood pressure changes

Medications to Avoid with MCAS

If you have MCAS, there are several medications that you need to avoid. These medications are associated with a high risk of release of mediators from mast cells. They may increase the symptoms of MCAS by increasing mast cell activation, triggering histamine release, increasing histamine intolerance, or inhibiting the function of the DAO enzyme, which breaks down histamine. Here is the list of medications that you and your doctor need to avoid using if you have MCAS and a list of potential alternatives that may support your health issue without further triggering MCAS (1, 2, 3).


General medications to avoid if possible with MCAS:

  • Alcohol

  • Amphotericin B

  • Anticholinergic drugs

  • Dextran

  • Dextromethorphan

  • Ethanol

  • Polymyxin B

  • Quinine

  • Vancomycin IV

  • Alpha-adrenergic blockers

  • Beta-adrenergic blockers

Potential substitutes: Depends on the medication in question


Pain medications to avoid with MCAS:

  • Opioid narcotics (may be tolerated by some individuals)

  • Toradol

  • Non-steroidal anti-inflammatory drugs (unless the patient is already taking a drug from this class)

Potential substitutes: Fentanyl (may require adjunct treatment with Zofran), Tramadol


Muscle relaxants to avoid with MCAS:

  • Atracurium

  • Doxacurium

  • D-tubocurarine

  • Metocurine

  • Mivacurium

  • Succinylcholine

  • Atracurium

  • Rocuronium

Potential substitutes: Pancuronium, Vecuronium


Local anasthetics to avoid with MCAS:

  • Benzocaine

  • Chloroprocaine

  • Articaine

  • Tetracaine

  • Procaine

Potential substitutes: Bupivacaine, Lidocaine, Mepicacaine, Prilocaine, Levobupivacaine, Ropivacaine


Intravenous narcotics to avoid with MCAS:

  • Methohexital

  • Phenobarbital

  • Thiopental

Potential substitutes: Propofol, Ketamine, Etomidate, Midazolam


Antibiotics to avoid with MCAS:

  • Cefuroxime

  • Gyrase inhibitors

  • Vancomycin

Potential substitutes: Roxithromycin


Selective dopamine and norepinephrine uptake inhibitors to avoid with MCAS:

  • Bupropion

Potential substitutes: Amitriptyline, doxepin, clomipramine, maprotiline


Selective serotonin uptake inhibitors to avoid with MCAS:

  • All (for example Prozac, Celexa, Zoloft, Paxil etc.)

Potential substitutes: none


Anticonvulsive agents to avoid with MCAS:

  • Carbamazepine

  • Topiramate

Potential substitutes: Clonazepam


Opioid analgesics to avoid with MCAS:

  • Meperidine

  • Morphine

  • Codeine

Potential substitutes: remifentanil, alfentanil, fentanyl, oxycodon, piritramid


Peripheral-acting analgesics to avoid with MCAS:

  • Acidic non-steroidal anti-inflammatory drugs such as ASS or ibuprofen

Potential substitutes: Paracetamol, metamizol


Peptidergic drugs to avoid with MCAS:

  • Icatibant

  • Cetrorelix

  • Sermorelin

  • Octreotide

  • Leuprolide

Potential substitutes: None


X-ray contrast medium to avoid with MCAS:

  • Iodinated contrast medium

  • Gadolinium chelate

Potential substitutes: Non-ionic contrast media: iohexol, iopamidol, iopromida, ioxilan, ioversol, idolatran, iodixanol


Plasma substitutes to avoid with MCAS:

  • Hydroxyethyl starch

  • Gelatine

Potential substitutes: Albumin solution, 0.9 %-NaCl solution, Ringer’s solution


Cardiovascular drugs to avoid with MCAS:

  • ACE inhibitors

  • ß-Adrenoceptor antagonists

Potential substitutes: Sartans, calcium channel antagonists, ivabradine, and many other options


Reactions to Medications May Be a Key to MCAS Diagnosis


Diagnosing MCAS can be complex. We have to look at your health history, your symptoms, and various health markers. Reactions to a medication may also serve as a clue to the diagnosis. You can try to recall if they’ve ever had a reaction to any or some of these drugs before visiting your doctor. When patients visit my office, I look out for such reactions when taking a history in a complex patient, to determine if indeed mast cell instability is an issue. Whether MCAS is the culprit or there are other underlying problems, if you have a reaction to a medication, always talk to your doctor.


Excipients and MCAS

Besides the medications I just listed, you have to watch out for certain excipients as well. Excipients are inactive ingredients in over-the-counter drugs, prescription medications, and vaccines. Excipients may play a variety of roles in medications, including delivering the active ingredient to your body or supporting the efficacy of the medication. The active ingredient usually takes up a tiny percentage of the medication. Most of it is excipients (4).

Though excipients are generally safe, they can cause problems for some people. If you have MCAS, certain excipients may lead to a serious reaction, anaphylaxis, and other issues. So even if you don’t have an issue with the active ingredient, some inactive excipients may cause a problem (5, 6, 7).


Types of Excipients

There are many kinds of excipients to be aware of and the list is ever-growing. The main categories include:

  • Lubricants, such as silica and magnesium stearate, can prevent pills from sticking together in the bottle

  • Binders and fillers, such as cellulose and polyethylene glycol, bind the ingredients together and are responsible for the volume of the pill

  • Coatings, such as gelatin and shellac, make swallowing easier and may also offer extended-release options

  • Dyes, such as FD&C Blue #2 and FD&C Red #5, simply provide the color to the drug

  • Flavorings, such as xylitol or sucralose, can make medications more pleasant tasting and mask bad-tasting ingredients

  • Preservatives, such as citric acid and retinol palmitate, are used for increasing shelf-life

Common Harmful Excipients



What excipients you are reacting to may depend on your health and body. The most common excipients that patients with MCAS tend to react to include:

  • Povidone

  • Dyes

  • Alcohol

  • Adhesives

What to Do if You Are Reacting to a Medication or Excipient with MCAS?

If you know that you have MCAS, symptoms of MCAS, or known problems with certain excipients, inform your doctor. If you are experiencing anaphylaxis or other serious reactions, seek immediate medical help. If you are experiencing less serious symptoms, talk to your doctor and discuss alternative options that are safe for MCAS.

If you are reacting to a medication that can trigger mast cell activation, your doctor will likely have to prescribe an alternative that is not a problem for those with MCAS or look for treatment options without the use of medication. If you are reacting to an excipient, the solution often lies in using a different version of the same medication without the specific excipient you are sensitive to or treatment options without medication.

Next Steps

1. Working with a healthcare practitioner knowledgeable in MCAS and histamine intolerance is the best way to get to the root cause of your symptoms and to create an individualized treatment plan. I welcome you to start a personalized functional medicine consultation with me. You may book your consultation here.


2. Check out my Histamine Intolerance Course here. Learn on your own time, from anywhere. Get an inside look at the most helpful functional medicine tests for pinpointing imbalances, ways to identify and manage the most common (and sometimes surprising) mast cell triggers, and learn what to eat, what to avoid, and why.