A pill imprinted with CTN 10 is an over-the-counter (OTC) and prescription-strength formulation of Cetirizine Hydrochloride 10 mg. It belongs to the class of medications known as second-generation antihistamines.
Pill Identification
Characteristic Specification
- Imprint Code –
CTN 10 - Active Ingredient – Cetirizine Hydrochloride (10 mg)
- Drug Class – Second-generation receptor antagonist
- Color – White
- Shape – Barrel / Bullet-shaped
- Size ~8 mm
- Score Line – Unscored
- Note: Pill imprints, shapes, and colors can vary slightly depending on the manufacturer. Always confirm the imprint code with a pharmacist or healthcare provider if you are uncertain about a medication.
Indications & Uses
The CTN 10 tablet is primarily prescribed or taken OTC to relieve symptoms associated with upper respiratory allergies and allergic skin conditions, including:
- Seasonal Allergic Rhinitis (Hay Fever): Sneezing, runny nose, nasal congestion, and itchy/watery eyes caused by outdoor allergens like pollen.
- Perennial Allergic Rhinitis: Year-round allergy symptoms triggered by indoor allergens such as dust mites, pet dander, and mold.
- Chronic Idiopathic Urticaria: Unexplained hives, swelling, and itching on the skin.
Mechanism of Action
During an allergic reaction, the immune system releases histamine, an endogenous chemical compound that binds to $H_1$ receptors on target cells. This binding causes classic allergy symptoms: smooth muscle contraction, increased vascular permeability (leading to swelling/runny nose), and stimulation of sensory nerves (causing itching).
- Selective Blockade: Cetirizine works as a potent, highly selective competitive antagonist of peripheral histamine receptors. By occupying these receptors, it blocks histamine from binding and triggering allergic inflammatory cascades.
- Low CNS Penetration: Unlike first-generation antihistamines (such as diphenhydramine), cetirizine exhibits lower lipid solubility and limited passage across the blood-brain barrier. Consequently, it produces significantly less sedation and cognitive impairment.
Dosage & Administration
Standard dosing guidelines according to official drug labels:
- Adults and Children 6 years and older:
- Take one 10 mg tablet once daily (every 24 hours) with or without food.
- Do not exceed one 10 mg tablet within a 24-hour period.
- A 5 mg dose (or a split dose if using scored tablets) may be sufficient for milder symptoms.
- Adults 65 years and older: Ask a doctor prior to use. Age-related reduction in kidney function may require a reduced dose (typically 5 mg daily).
- Children under 6 years of age: Consult a pediatrician. (Liquid or chewable formulations are generally preferred for younger children).
- Renal or Hepatic Impairment: Patients with compromised liver or kidney function require dosage adjustment (usually 5 mg once daily) and should consult a doctor before starting treatment.
Side Effects
Although cetirizine is generally well-tolerated, side effects can occur:
Common Side Effects
- Somnolence / Drowsiness: Occurs in ~10–14% of users (higher than other second-generation antihistamines like loratadine, but lower than first-generation options).
- Dry Mouth
- Headache
- Fatigue or Tiredness
- Gastrointestinal discomfort (nausea, mild abdominal pain)
Severe or Rare Reactions (Seek Immediate Medical Care)
- Severe Hypersensitivity: Anaphylaxis, angioedema (swelling of the face, lips, tongue, or throat), or difficulty breathing.
- Urinary Retention: Difficulty urinating or painful urination.
- Severe Dizziness or Syncope (Fainting)
Precautions & Interactions
- Central Nervous System Depressants & Alcohol: Avoid consuming alcoholic beverages while taking cetirizine. Concurrent use with alcohol, sedatives, or tranquilizers can worsen drowsiness and impair motor coordination.
- Driving & Operating Machinery: Because drowsiness can occur, assess your individual response to the medication before driving, operating heavy machinery, or performing hazardous tasks.
- Allergy Skin Testing: Cetirizine suppresses histamine-mediated skin responses. Discontinue the medication at least 3 to 4 days before undergoing skin prick tests to prevent false-negative results.
- Discontinuation Rebound (Pruritus): In rare cases, abruptly stopping daily cetirizine after prolonged use (several months) can trigger severe, temporary generalized itching (rebound pruritus). Tapering the dose with guidance from a doctor can help prevent this.
Warnings & Contraindications
- Contraindications: Do not use if you have a known history of severe allergic reactions to cetirizine, hydroxyzine, or any inactive ingredients in the tablet.
- Pregnancy & Breastfeeding:
- Pregnancy: Consult a physician before use. Cetirizine is typically considered low-risk during pregnancy, but medical clearance is recommended.
- Breastfeeding: Cetirizine passes into breast milk and is generally not recommended while nursing without medical advice, as it may cause drowsiness in a infant.
- Overdose: An overdose may cause extreme drowsiness, confusion, or agitation (especially in children). In the event of an accidental overdose, contact a local Poison Control Center or emergency services immediately.