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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Cetirizine Hydrochloride, Pseudoephedrine Hydrochloride
Brand Name
Allergy Relief D12
Generic Name
Cetirizine Hydrochloride, Pseudoephedrine Hydrochloride
Active Ingredient
CetirizineCategory
Histamine-1 Receptor Antagonist [EPC]
Salt Form
Hydrochloride
Variants
2
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Allergy Relief D12, you must consult a qualified healthcare professional.
Detailed information about Allergy Relief D12
Cetirizine is a potent, second-generation antihistamine used to treat allergic rhinitis and chronic urticaria. As a selective H1 receptor antagonist, it provides rapid relief from allergy symptoms with a significantly lower risk of sedation compared to first-generation antihistamines.
For adults and adolescents aged 12 years and older, the standard recommended dose of cetirizine is 5 mg to 10 mg taken orally once daily.
Cetirizine is approved for use in children as young as 6 months, but the dosage must be carefully calibrated based on age:
Because cetirizine is primarily cleared by the kidneys, patients with decreased kidney function require lower doses to prevent drug accumulation and toxicity:
In patients with impaired liver function, the metabolism of cetirizine is not significantly affected, but the overall clearance may be reduced. A dose of 5 mg once daily is generally recommended for patients with significant hepatic impairment.
Patients aged 65 and older may have undiagnosed reductions in renal function. It is often recommended to start at 5 mg once daily and monitor for increased side effects, particularly sedation and confusion.
If you miss a dose, take it as soon as you remember. If it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not take two doses at once to make up for a missed one, as this increases the risk of side effects.
An overdose of cetirizine typically manifests as extreme somnolence. In children, an overdose may initially cause agitation or restlessness followed by extreme drowsiness.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or the frequency of use without medical guidance, especially when treating children or the elderly.
While cetirizine is generally well-tolerated, some individuals may experience side effects. The most frequently reported side effect is somnolence (drowsiness). Although marketed as a second-generation antihistamine, clinical trials showed that approximately 13.7% of patients taking 10 mg of cetirizine experienced drowsiness, compared to 6.3% of those taking a placebo.
Other common effects include:
Cetirizine is a highly effective medication, but it must be used with caution in specific circumstances. The most critical safety point is the potential for Central Nervous System (CNS) depression. While cetirizine is less likely to cause sedation than older antihistamines, it can still impair mental alertness and physical coordination. Patients should be aware of how they react to the medication before engaging in hazardous activities.
There are currently no FDA black box warnings for cetirizine. It does not carry the high-risk profile associated with medications that require such warnings, such as certain antidepressants or blood thinners.
There are no absolute contraindications for drug-drug combinations that result in fatal outcomes, but the following should be strictly avoided due to severe risk:
Cetirizine must NEVER be used in the following circumstances:
Cetirizine was previously classified as FDA Pregnancy Category B. This means that animal reproduction studies have failed to demonstrate a risk to the fetus, and there are no adequate and well-controlled studies in pregnant women.
Cetirizine is excreted in human breast milk. Studies estimate that a nursing infant receives approximately 1% to 3% of the maternal weight-adjusted dose.
Cetirizine is a highly potent and selective antagonist of the peripheral H1 receptors. Its primary mechanism involves competing with free histamine for binding sites on effector cells. Unlike first-generation antihistamines, cetirizine has a very low affinity for the H1 receptors in the brain.
Furthermore, cetirizine has been shown to have anti-inflammatory properties beyond simple H1 antagonism. At therapeutic doses, it inhibits the late-phase recruitment of inflammatory cells, particularly eosinophils, to the site of an allergic reaction. It also reduces the expression of adhesion molecules like ICAM-1, which are necessary for inflammatory cells to migrate into tissues. This dual action makes it particularly effective for chronic allergic conditions.
Common questions about Allergy Relief D12
Cetirizine is primarily used to relieve symptoms of seasonal and perennial allergic rhinitis, such as sneezing, runny nose, and itchy eyes. It is also highly effective in treating chronic idiopathic urticaria, which are hives that occur without a known cause for six weeks or longer. By blocking H1 receptors, it prevents histamine from causing the inflammation and irritation associated with these conditions. Many doctors also recommend it for pet or dust mite allergies. It is available both as a prescription and over-the-counter for these uses.
The most common side effect of cetirizine is drowsiness, affecting approximately 10-14% of users. Other frequent side effects include dry mouth, fatigue, and dizziness. In children, it may cause stomach pain or headaches. While it is a second-generation antihistamine designed to be non-sedating, it is more likely to cause sleepiness than fexofenadine or loratadine. Most of these effects are mild and resolve as the body adjusts to the medication.
It is strongly recommended that you avoid alcohol while taking cetirizine. Alcohol can enhance the central nervous system depressant effects of the medication, leading to severe drowsiness and impaired coordination. This combination can make activities like driving or operating machinery extremely dangerous. Even small amounts of alcohol can interact with cetirizine to cause more significant impairment than either substance alone. Always consult your doctor before mixing any medication with alcohol.
Cetirizine is generally considered one of the safer antihistamines to use during pregnancy and was formerly classified as Category B by the FDA. Large-scale studies have not found a link between cetirizine use and an increased risk of birth defects. However, it should only be used when the benefits outweigh the potential risks to the fetus. Most healthcare providers recommend trying non-drug treatments first, such as saline nasal sprays. Always talk to your OB/GYN before starting cetirizine while pregnant.
Cetirizine is known for its rapid onset of action, with most patients experiencing symptom relief within 20 to 60 minutes. Peak levels of the drug in the bloodstream are typically reached within one hour of taking a dose. This makes it faster-acting than some other second-generation antihistamines like loratadine. The effects of a single dose are designed to last for a full 24 hours. For best results in chronic cases, it should be taken consistently at the same time each day.
For most people, stopping cetirizine suddenly is safe and does not cause problems. However, some long-term users have reported intense itching, known as pruritus, after stopping the drug abruptly. This 'rebound' effect occurs because the body's H1 receptors become sensitized after being blocked for a long time. If you have been taking cetirizine daily for several months, it is often better to gradually reduce the dose over a week or two. If you experience severe itching after stopping, contact your healthcare provider.
If you miss a dose of cetirizine, take it as soon as you remember. However, if it is nearly time for your next scheduled dose, skip the missed one and continue with your regular timing. You should never take two doses at the same time to compensate for a missed one, as this increases the risk of side effects like extreme drowsiness. Since cetirizine lasts for 24 hours, missing one dose may lead to a temporary return of allergy symptoms. Maintaining a consistent schedule helps keep the medication levels stable in your body.
Weight gain is not a commonly reported side effect of cetirizine in short-term clinical trials. However, some long-term observational studies have suggested a potential link between chronic antihistamine use and increased body mass index (BMI). This may be because H1 receptors play a role in regulating appetite and metabolism in the brain. While the risk is considered low, if you notice unexplained weight gain while taking cetirizine, you should discuss it with your doctor. Most patients do not experience significant weight changes with standard use.
Cetirizine has fewer drug interactions than many other medications because it is not metabolized by the liver's CYP450 enzymes. However, it can interact with other CNS depressants like sleeping pills, opioid pain relievers, and muscle relaxants, increasing sedation. It may also interact with theophylline, a medication used for respiratory issues. You should avoid taking it with other antihistamines unless specifically told to do so by a doctor. Always provide your healthcare provider with a full list of your current medications to ensure safety.
Yes, cetirizine is widely available as a generic medication and is significantly less expensive than brand-name versions like Zyrtec. Generic cetirizine is required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. It must also prove bioequivalence, meaning it works in the body the same way. Many consumers find that generic cetirizine provides the same level of allergy relief at a fraction of the cost. It is available in various forms, including tablets, liquids, and chewables.
Other drugs with the same active ingredient (Cetirizine)
These effects occur in a smaller subset of the population but are still documented in clinical literature:
Rarely, patients may experience more unusual reactions:
> Warning: Stop taking Cetirizine and call your doctor immediately or seek emergency care if you experience any of the following:
Cetirizine is generally considered safe for long-term use when taken as directed. However, some patients report a phenomenon known as 'Cetirizine Withdrawal Pruritus'. Upon suddenly stopping the medication after months or years of daily use, some individuals experience intense, generalized itching (pruritus) that can last for several days to weeks. This is not an allergy to the drug itself but a rebound effect of the H1 receptors. Tapering the dose slowly under medical supervision can help prevent this.
No FDA black box warnings exist for Cetirizine. It is considered to have a high safety profile for the general population when used according to the label instructions.
Report any unusual symptoms or side effects to your healthcare provider. Monitoring your body's response during the first few days of treatment is essential to ensure the medication is both safe and effective for you.
For most healthy individuals taking cetirizine over-the-counter, routine lab monitoring is not required. However, for those with chronic conditions:
Exercise caution when driving a motor vehicle or operating heavy machinery until you are reasonably certain that cetirizine does not make you drowsy. Clinical studies show that at the 10 mg dose, a measurable percentage of the population experiences enough sedation to potentially impair reaction times.
Avoid the consumption of alcohol while taking cetirizine. Alcohol can significantly increase the sedative effects of the medication, leading to dangerous levels of drowsiness, impaired judgment, and loss of motor control. This additive effect is one of the most common causes of adverse events involving second-generation antihistamines.
For most users, cetirizine can be stopped abruptly without issue. However, as noted in the side effects section, long-term users (those taking it daily for >6 months) may experience rebound itching. If you have been on cetirizine long-term, consider reducing your dose to 5 mg for a week, then 2.5 mg for another week before stopping entirely.
> Important: Discuss all your medical conditions, including any history of kidney or liver disease, with your healthcare provider before starting Cetirizine.
Mechanism of Interactions: Most cetirizine interactions are pharmacodynamic (the drugs have additive effects on the body) rather than pharmacokinetic (the drugs change how the other is metabolized). Because cetirizine bypasses the liver's CYP450 system, it is much safer than many other medications in terms of metabolic interference.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. A complete medication reconciliation is the best way to prevent dangerous interactions.
These are conditions where the drug should only be used if the benefits clearly outweigh the risks, and only under strict medical supervision:
Patients should be aware of cross-sensitivity within the piperazine derivative class of antihistamines. If you have had an adverse reaction to medications like meclizine (used for vertigo) or cyclizine, you should inform your doctor before starting cetirizine, as these drugs share similar chemical backbones.
> Important: Your healthcare provider will evaluate your complete medical history, including kidney function and previous drug allergies, before prescribing Cetirizine or recommending it for OTC use.
Cetirizine is approved for pediatric use in children as young as 6 months. It is widely considered safe and effective for treating allergic rhinitis and hives in children.
In patients aged 65 and older, the half-life of cetirizine is prolonged by approximately 50%, and the clearance is reduced by 40%.
As the kidneys are the primary route of elimination, dosing must be adjusted based on the patient's Creatinine Clearance (CrCl):
In patients with chronic liver disease, the clearance of cetirizine is reduced. A maximum dose of 5 mg once daily is typically recommended for those with significant hepatic dysfunction (Child-Pugh Class B or C).
> Important: Special populations require individualized medical assessment. Never start a new medication for a child, elderly person, or during pregnancy without consulting a healthcare professional.
| Parameter | Value |
|---|---|
| Bioavailability | ~70% |
| Protein Binding | 93% |
| Half-life (Adults) | 8.3 hours |
| Half-life (Children) | 6-7 hours |
| Tmax (Time to peak) | 1.0 hour |
| Metabolism | Minimal (Non-CYP) |
| Excretion | Renal 70%, Fecal 10% |
Cetirizine is classified as a Second-Generation Antihistamine and a Piperazine Derivative. It is chemically related to hydroxyzine but lacks the significant CNS penetration and anticholinergic activity of its parent compound. Related medications in this class include levocetirizine, loratadine, and fexofenadine.