Antihistamines Can Worsen MS-Related Fatigue

Fatigue can be a side effect of these medications

Antihistamines in a blister pack.
Antihistamines in a blister pack. BSIP/UIG/Getty Images

Fatigue is common when dealing with multiple sclerosis (MS). In fact, an estimated 70% of people with MS say that fatigue is their most disabling symptom. While much of it comes from the disease process itself or MS-related heat intolerance, there are many secondary causes of fatigue in MS. One contributing factor could actually be some of the medications that you are taking to slow your MS or deal with specific symptoms.

If you suffer from MS-related fatigue, it is important to investigate all possible causes, including side effects from some of your medications.

Use of Antihistamines By People With Multiple Sclerosis

Histamines are chemicals released by the body’s inflammatory cells during an allergic reaction, which results in classic allergy symptoms such as itching, sneezing, runny nose, congestion and irritated eyes. Antihistamines block the actions of these histamines, thereby reducing the allergic response.

Many of us have allergies from time to time, and antihistamines can make us much less miserable. You should know, however, that antihistamines can contribute to fatigue, even if they are used as nasal sprays or eye drops. Also, be aware that many of these can be purchased over-the-counter but still have side effects.

They are commonly mixed in with other medications to provide multi-symptom relief, such as cold and flu medications, and often available as “store brands,” so look carefully at the list of active ingredients.

They are also often specifically added to other drugs (Tylenol PM or NyQuil) to help people sleep. Be aware that even some of the “nondrowsy” allergy medications can still affect those of us struggling with MS-related fatigue enough to be noticed.

The bottom line is to use antihistamines wisely. Speak with your neurologist if you suspect that your fatigue is worsened by the use of your antihistamines, maybe he or she can help you find another solution.

But “Fatigue” Isn’t Listed as a Side Effect of My Drug

Most of the medications listed below have “tiredness” or “drowsiness” as a potential side effect. Some list “dizziness” or “weakness.” Others also have side effects, such as sweating, trembling, difficulty breathing, lightheadedness, flushing, confusion, nausea/vomiting, or fainting spells. For someone that does not have MS, many of these effects could just be a passing annoyance. For those of us, though, who battle MS-related fatigue on a daily basis, any of the discomforts listed above may be enough to tip the balance between a good day and a bad day, fatiguewise.

List of Antihistamines that Can Contribute to Fatigue in People with MS

Note to My Non-U.S. Friends: The list below includes brand names of drugs prescribed in the United States. For people in other countries, please refer to the generic name of the medication, which may be spelled differently depending on the country. Thanks for your understanding.

Azelastine (Astelin): An antihistamine that is available as an eye solution or nasal spray.

Cetirizine (Zyrtec): An antihistamine that is used to treat both seasonal and year-round allergies as well as to treat hives and chronic itchy skin. It is available as chewable tablets, oral syrup or tablets.

Chlorpheniramine (Aller-Chlor, Chlor-Trimeton, and Teldrin as an ingredient in many store brands of allergy medicines): An antihistamine used to treat symptoms of allergies and colds. It is available as oral syrup, effervescent tablets, tablets or capsules.

Diphenhydramine (Benedryl): An antihistamine that reduces allergic reactions and vertigo, available as an injection, oral syrup or elixir, solution, tablets or capsules. It is also found in many types of cold medications or nighttime pain relief medicine (Advil PM, Tylenol PM) to help people sleep.

Loratadine (Claritin): An antihistamine to help relieve allergy symptoms, such as hay fever and itching. It is available as oral syrup or solution or tablets.

Phenylephrine (Neo-Synephrine): Specifically for eye allergies or symptoms, available as eye solution, nose drops, spray, jelly, quick-dissolve strips or tablets.

Doxylamine (Unisom Sleeptabs, NyQuil, many store brands): This is an antihistamine that is primarily used as a sleep aid, either added to other medications or by itself. It is available as tablets, capsules or syrups.

How to Manage Medication Fatigue

Just because it looks like one of your medications may be contributing to your fatigue, doesn’t necessarily mean it is the end of the drug for you. Ask your doctor for help figuring this out. He or she may have some ideas about taking it at a different time of day or taking it with food. Maybe splitting the dose would reduce the side effects or maybe it comes in a different form, such as a time-released version, that may be better for you. If none of these things seem like they will work, there may be all sorts of other things that the doctor can try, such as other medications or other types of therapy.

Think About Interactions Too: Maybe your medication wouldn’t cause fatigue if you didn’t take it at the same time as your other medications. Maybe it is not a good idea to wash it down with a margarita. Ask your doctor about these things.

Keep a Fatigue Log: When you are trying to pinpoint possible causes or contributors to your fatigue, it is important to keep a record of what you are experiencing, so that you can discuss it with your doctor. Make sure that you include your medications and when you took them.

But It’s Not a Pill: Even if your drug is not in tablet or injection form, it can still cause fatigue. Remember, patches, eye drops, nasal sprays and other methods of delivering medications are still getting the active ingredients into your bloodstream in most cases. Simply put, if it can help a symptom and have a positive effect, it can also have side effects.

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