Claritin-D contains two active ingredients: loratadine, an antihistamine, and pseudoephedrine sulfate, a nasal decongestant. The “D” stands for decongestant, which is what separates it from regular Claritin (loratadine only). It comes in two formulations: a 12-hour version with 5 mg of loratadine and 120 mg of pseudoephedrine, and a 24-hour version with 10 mg of loratadine and 240 mg of pseudoephedrine.
The Two Active Ingredients
Each ingredient in Claritin-D targets a different part of allergy misery. Loratadine handles the sneezing, itching, and runny nose by blocking histamine receptors throughout your body. Pseudoephedrine tackles the stuffed-up feeling by shrinking swollen blood vessels inside your nasal passages, which opens up your airways and lets you breathe again.
Loratadine is a second-generation antihistamine, meaning it was specifically designed to work without making you drowsy. Older antihistamines like diphenhydramine (Benadryl) easily pass into the brain, where they block histamine receptors that help keep you alert. Loratadine’s chemical structure was modified to largely keep it out of the brain, so it controls allergy symptoms with minimal sedation.
Pseudoephedrine works differently. It stimulates receptors on blood vessels in your nasal lining, causing them to constrict. When those vessels tighten, the swollen tissue shrinks and congestion clears. It also triggers norepinephrine release in nerve endings, which adds to the decongestant effect. This stimulant action is why pseudoephedrine can make some people feel jittery or have trouble sleeping.
12-Hour vs. 24-Hour Formulations
The two versions aren’t just different doses taken at different intervals. The 12-hour tablet contains 5 mg of loratadine and 120 mg of pseudoephedrine, taken twice daily. The 24-hour tablet doubles both amounts (10 mg loratadine, 240 mg pseudoephedrine) in a single extended-release tablet designed to meter out the medication over a full day. Both are approved for adults and children 12 years and older.
Common Side Effects
Most side effects from Claritin-D come from the pseudoephedrine, not the loratadine. Because pseudoephedrine is a stimulant, it can cause insomnia, nervousness, restlessness, dry mouth, dizziness, and headache. Some people notice palpitations or a racing heartbeat. Less common effects include nausea, stomach pain, constipation, loss of appetite, and blurred vision.
Loratadine on its own typically causes only mild headache or occasional drowsiness. But combined with pseudoephedrine, the stimulant effects tend to dominate. If you’re sensitive to caffeine or other stimulants, you’ll likely notice the pseudoephedrine component.
Pseudoephedrine can raise blood pressure, so Claritin-D is not appropriate for people with severe or uncontrolled hypertension. This is a key difference from regular Claritin, which does not typically affect blood pressure. You should also avoid Claritin-D if you’ve taken an MAO inhibitor (a type of antidepressant) within the past two weeks, as the combination can cause a dangerous spike in blood pressure.
Why You Need an ID to Buy It
Claritin-D sits behind the pharmacy counter, not because it requires a prescription, but because pseudoephedrine can be chemically converted into methamphetamine. The Combat Methamphetamine Epidemic Act of 2005 limits purchases to 3.6 grams of pseudoephedrine base per day and 9 grams per 30-day period. You’ll need to show a government-issued photo ID, and the pharmacy logs each purchase electronically. This applies to every product containing pseudoephedrine, not just Claritin-D.
For context, a single box of Claritin-D 24 Hour (15 tablets) contains about 3.6 grams of pseudoephedrine, so buying two boxes in one day would put you at the daily limit. Most people taking the medication as directed won’t run into issues, but if you’re buying for multiple family members, you may hit the monthly cap.
How It Differs From Regular Claritin
Regular Claritin contains only loratadine. It relieves sneezing, itchy or watery eyes, and a runny nose, but it does nothing for congestion. If your main complaint is a stuffed-up nose from allergies or a cold, the loratadine alone won’t help much. That’s the gap pseudoephedrine fills in Claritin-D.
The trade-off is a longer list of potential side effects, the behind-the-counter purchase requirement, and restrictions for people with high blood pressure or certain heart conditions. If you don’t have significant congestion, regular Claritin is the simpler, lower-risk option. If congestion is your primary symptom, the pseudoephedrine component is specifically what you need.