Key takeaways

Claritin-D is contraindicated in patients using MAOIs because of the increased risk of hypertensive crisis.
Other medications, including antihistamines, antibiotics, and cimetidine, have a mild interaction with Claritin.
Talk to your healthcare provider about all your medications to avoid possible drug interactions.

In this article:

In this article

Claritin (loratadine) is an over-the-counter antihistamine used to treat allergic reactions or allergic rhinitis and their associated symptoms, including sneezing, runny nose or stuffy nose, watery eyes, itchy throat, and hives.

Claritin interacts with other medications, such as monoamine oxidase inhibitors, other antihistamines, and antibiotics. Claritin is not known to interact with alcohol, but precaution is advised when it is taken together. Given the risk of unwanted effects associated with drug-drug interactions, it’s essential to know how Claritin, when combined with other drugs, may affect effectiveness, such as increasing or decreasing the effects of the different medicines.

Claritin drug interactions

Here’s a look at potential drug interactions with Claritin and possible side effects that may occur:

Drug class or group name	Drug name	Interactions/side effects
Monoamine oxidase inhibitors	Azilect Rasagiline Emsam Nardil Parnate Xadago	Very high blood pressure when taken with Claritin-D specifically
Antihistamines	First-generation: Benadryl, Phenergan, Atarax Second-generation: Zyrtec, Allegra, Xyzal	Can exacerbate side effects
H2 Blockers	Cimetidine	Increase Claritin blood levels
Antibiotics	Erythromycin Clarithromycin	Increase Claritin blood levels
Anticonvulsants	Carbamazepine Phenytoin	Decrease Claritin blood levels

Monoamine oxidase inhibitors

Monoamine oxidase inhibitors (MAOIs) are drugs prescribed for treating depression, emotional conditions, Alzheimer’s disease, and Parkinson’s disease. Claritin-D contains the active ingredients loratadine (antihistamine) and pseudoephedrine sulfate (nasal decongestant).

MAOI and the pseudoephedrine sulfate component of Claritin-D may interact to cause very high blood pressure that leads to hypertensive crisis in severe cases. Symptoms include heart palpitations, chest pain, severe headache, confusion, sudden facial droop, and slurred speech. Therefore, Claritin-D is not recommended for individuals taking MAOIs. You should also avoid using Claritin-D for the first 14 days after discontinuing MAOIs; however, plain Claritin does not interact with MAOIs.

Examples of MAOIs include:

Azilect (rasagiline)
Emsam (Selegiline)
Nardil (phenelzine)
Parnate (tranylcypromine)
Xadago (Safinamide)

Notify your healthcare provider if you use any of the listed medications.

Antihistamines

Antihistamines are a class of medications that block the actions of histamine in the body and are used to treat allergy symptoms. Combining and taking different antihistamines at the same time can compound the side effects of these medications, eventually leading to antihistamine toxicity, with symptoms such as increased drowsiness, confusion, gastrointestinal agitation, and fast heartbeat.

Antihistamines that your healthcare provider may prescribe include:

First-generation antihistamines: Diphenhydramine (Benadryl), Promethazine (Phenergan), Hydroxyzine (Atarax)
Second-generation antihistamines: Cetirizine (Zyrtec), Fexofenadine (Allegra), Levocetirizine (Xyzal)

For example, mixing Benadryl and Claritin triggers symptoms such as drowsiness, constipation, blurred vision, and dry mouth. “Claritin and Benadryl are both antihistamines. Because they are in the same category, I wouldn’t say they interact, but they have an additive effect. I advise my patients not to take these two together regularly. If they need to, they may feel more side effects like drowsiness,” says Maaz Jalil, DO, board-certified pediatric and adult allergist and immunologist, with ENT and Allergy Associates, Medford, NJ.

Occasionally, your healthcare provider may recommend using first-generation antihistamines, such as Benadryl, at night and second-generation antihistamines, like Claritin, during the day. However, it is a good idea only to do this when recommended by a healthcare professional.

H2 Blockers

Cimetidine belongs to the drug class H2 blockers, and it is an oral over-the-counter medication used to treat symptoms of indigestion, such as heartburn.

“Cimetidine is also an antihistamine, but it works on a different receptor important for stomach acid secretion,” says John Boyle, MD, ENT physician with Wilmington Health at Parker Farm Drive, Mayfaire.

“Despite this, there is an interaction as it relates to the metabolism of the medication. Cimetidine can interfere with an enzyme that breaks down Claritin. Taking both can increase the level of effect of Claritin due to decreased clearance,” Dr. Boyle says. However, researchers noted that it does not affect the safety of Claritin.

Antibiotics

Antibiotics are a class of medications for treating bacterial infections. Mixing some antibiotics with Claritin can increase blood levels of the latter, because it affects the intestinal enzyme CYP3A4, which is involved in its metabolism and clearance. Researchers noted that this interaction does not affect the safety of Claritin.

Below are some antibiotics that may interact with Claritin:
Erythromycin
Clarithromycin

Additionally, antifungals like ketoconazole interact with Claritin in a manner similar to the antibiotics mentioned previously. Inform your healthcare provider if you are on antibiotics or antifungals; they will give you appropriate medical advice on how to use both and avoid drug-drug interactions.

Anticonvulsants

Anticonvulsants are medications used to treat seizures or convulsions. Carbamazepine and phenytoin are prescription anticonvulsant drugs that may lower blood levels of Claritin when used in combination, potentially affecting its effectiveness. To avoid this drug interaction, speak with your healthcare provider; they may suggest an alternate anticonvulsant or suggest an appropriate way/dose to take the medications.

Other Claritin interactions

Apart from drug interactions, be mindful of taking Claritin with alcohol, caffeine, herbal supplements, and in conditions such as kidney and liver disease. It’s generally considered safe, but you may need medical advice from a healthcare professional on how to best avoid potential interactions with Claritin.

Claritin and alcohol

Based on studies conducted to investigate the impact of combining Claritin and alcohol on driving, the researchers found that it did not impair alertness. At high doses of 40 mg of loratadine and 0.75 g/kg, Claritin did not reduce coordination. And, when compared to older antihistamines, triprolidine and alcohol significantly impaired driving performance, but not Claritin and alcohol. That said, it’s still best to follow the long-standing advice of avoiding alcohol when taking antihistamines.

Claritin and caffeine

“I don’t have any concerns with caffeine and Claritin together,” Dr. Jalil says. “However, Claritin-D contains a decongestant- pseudoephedrine, which is a stimulant, and that, along with caffeine, another stimulant, can increase the risk of side effects like high blood pressure, jitteriness, and palpitations. I recommend that you don’t take decongestants daily due to their effects on the heart.”

Claritin and diseases

“Preexisting liver and kidney conditions affect how Claritin is metabolized and excreted, so they can impact pharmacokinetics, causing the drug and its byproducts to accumulate in the body and increase the risk of side effects,” Dr. Jalil says. “There are other rare health conditions, such as phenylketonuria (PKU), and certain heart arrhythmias, which should be disclosed to your physician since they can interact with Claritin,” he adds.

Additionally, if you have heart disease, thyroid disease, high blood pressure, or trouble urinating, discuss with your healthcare provider before using Claritin or Claritin-D.

Claritin and herbal supplements

Research on interactions between Claritin and herbal supplements is limited, so there isn’t enough reliable information. Individuals taking herbal supplements should inform their healthcare provider, especially if the supplements have sedative properties, since antihistamines like Claritin may increase those effects.

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