What Medication Can You Not Take With Antihistamines

Overview

What medicine should you not take with antihistamines? 

Some medicines can cause problems when taken together with antihistamines. These medicines include antidepressants, stomach ulcer or indigestion medicines, and cough and cold remedies can contain an antihistamine (like Benylin Night or Vicks NyQuil).¹

What is an antihistamine

Antihistamines are a class of pharmaceutical medicines that you use to alleviate symptoms caused by allergies or colds, like watery or itchy eyes, sneezing, and a runny nose. They can also give you some relief when you suffer from hives or have a reaction on your skin from insect bites or stings. Especially when these symptoms are caused by a histamine release in your body. Histamine is a chemical messenger, and antihistamines will block the effects of this messenger.^1,2

Histamine is typically released when your body is trying to ward off something harmful, like an infection or parasite, and it will result in swelling of tissues and dilation of your blood vessels. However, if you suffer from allergies, your body will mistake something that is not harmful for something that is and will release histamine. This is how people with allergies have an allergic reaction to something harmless, like pollen, animal dander, or house dust (allergens). Their symptoms usually include itchy, watery eyes, allergic rhinitis, sneezing, and skin rashes.

You can take an antihistamine as a prophylaxis before you come into contact with an allergen, or you can take them afterwards to reduce the severity of your symptoms.^1,2

There are many types of antihistamines out there. Most of them you can buy over the counter without a prescription, but some of the stronger ones will need a prescription from your doctor.¹

There are two types of antihistamines. The first class is known to bind to the Histamine-1 (H-1) receptors. These tend to be used to treat histamine-mediated conditions, like allergies, as described above. The class of antihistamines that bind to the Histamine-2 (H-2) receptors can be used to treat upper gastrointestinal conditions that are caused by an excess of stomach acid.²

The H-1 antihistamines are typically found to be divided into two groups: the ones that may cause drowsiness or sleepiness, i.e. sedating antihistamines (first generation), and the ones that do not: the non-drowsy antihistamines or non-sedating antihistamines (second generation).

The ones that make you feel sleepy include, chlorphenamine (Piriton), cinnarizine, diphenhydramine (Benadryl), hydroxyzine, and promethazine.^2,3

The first-gen antihistamines work for about 4 to 6 hours, and thankfully the second-gen antihistamines are active for about 12 to 24 hours.²

In the non-drowsy category, we find acrivastine (Benadryl allergy relief), cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin).They are available as tablets, capsules, liquids, syrups, nasal sprays, eyedrops, creams, lotions, and gels.¹

In certain cases, you may find that you were prescribed antihistamines to help treat your insomnia or for long-term bad indigestion.² The use of the H-2 antihistamines is seen to significantly reduce stomach acid secretions.²

How to use oral antihistamine?

Take your medicines as advised by your doctor or pharmacist. If you have gotten yours over the counter, please read the instructions in the leaflet that comes with it and follow these instructions. 

It is important that you ensure yourself that you know:

• How to take them, with water or with food? 
• How much to take, as the dose might vary depending on age or weight
• When to take it, as some may need to be taken before bedtime. However, it is also important to know how many times a day you should be taking them
• How long to take them for, as some, you can take for an extended period of time while others are recommended for only a few days
• What to do in case you miss a dose, or if you overdose.

If you have any doubts whatsoever, please ask a pharmacist or your doctor.¹

Side Effects

Antihistamines are a type of medicine, and like all other medicines, they can cause side effects.

The most obvious side effect is that the drowsy type can cause drowsiness, make you sleepy and reduce your reaction speed. In some people, it will also reduce their coordination and impair their judgment. It is very important that when you take these antihistamines, you do not drive your car, operate (heavy) machinery or make important decisions. Typically, medicines causing these side effects will have a red warning sticker on their box just to make sure you take caution. 

Other side effects are:

• Being thirsty or having a dry mouth
• Blurred vision
• Having difficulty peeing

The non-drowsy type can also cause side effects, like:

• Headaches
• Having dry mouth
• Feeling sick
• Nervousness
• Dizziness
• Insomnia
• And in rare cases, can cause drowsiness.

It is important for you to check the leaflet that comes with your medicines: so you know what the possible side effects are and when you need to seek medical help.

Additionally, if you think yours has caused an unwanted side effect, you can report it to help others through the Yellow Card Scheme (in the U.K.).^1-3

Precautions

Do take extra care when you are taking other medicines already and want to add antihistamines. It is best to speak to your doctor or pharmacist before doing so, as there could be a risk you are taking with medicines that do not mix. This could stop them both from working properly or increase the risk of causing side effects.

Also speak to your doctor or pharmacist if you are:

• Pregnant or breastfeeding
• Looking for antihistamines for a young child
• Already taking other medicines!
• Having other health conditions, like heart disease (including arrhythmias), liver disease, kidney disease, or epilepsy.^1,3 you
• More contraindications of taking antihistamines include high blood pressure (hypertension) and increased ocular pressure (glaucoma).

Interactions

If you are on antidepressants, medicines for indigestion or a stomach ulcer, or taking cough and cold remedies that also contain an antihistamine, please consult your doctor or pharmacist as you might be taking on unnecessary risk.

Stay clear from drinking alcohol too when you are taking antihistamines, as it can increase the chances of you feeling sleepy. Especially if you are taking the type that makes you drowsy to start with!

Other drinks or food should be fine as they should not affect most antihistamines but do check the leaflet that comes with the medicine just to make sure.^1-3 

Oral Antihistamine Interaction With Other Drugs

Antihistamines may interact with other drugs that cause drowsiness, like sleeping medications, narcotic pain medication, sedatives, muscle relaxants, and seizure medications.

Additionally, drugs like tricyclic antidepressants, antipsychotics, and certain drugs that prevent vomiting (prochlorperazine) are also listed here.³

Which group of drugs has an interaction with antihistamines?

Drugs that make you feel sleepy or drowsy.³

When to stop taking antihistamines?

Take the antihistamines as advised by your doctor or pharmacist or leaflet’s instructions.
When experiencing side effects, stop taking the antihistamine and seek medical advice.¹

Question to ask medical specialist

Good questions to ask your medical specialist: 

• How to take the antihistamine, with water or with food? 
• How much to take, as the dose might vary depending on your age or weight
• When to take it, as some may need to be taken before bedtime. However, it is also important to know how many times a day you should be taking them
• How long to take them for, as some, you can take for a long period of time while others are recommended for only a few days
• What to do in case you miss a dose or if you overdose.
• When to seek medical help
• Can I take these while taking other medicines/herbal supplements?
• Can I take these while pregnant/breastfeeding?
• Are these safe to take, even with my underlying health issues?¹

Summary

Antihistamines are a medicine that you can use to alleviate symptoms caused by allergies or colds, like itchy eyes, nose and throat, sneezing, a runny nose, and skin rashes. They are very effective in giving relief and are relatively safe. Still, you have to take caution when taking them if you are already taking other medicines or have underlying health conditions. If you have any doubts about how to take these medicines, do speak to your doctor or pharmacist and ask them all the questions you have, and these are listed above so you are absolutely clear on how to take them and for how long.