ZYRTEC-D 12 HOUR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZYRTEC-D 12 HOUR (ZYRTEC-D 12 HOUR).
Cetirizine is a second-generation antihistamine that selectively inhibits peripheral H1 receptors, reducing histamine-mediated allergic responses. Pseudoephedrine is a sympathomimetic amine that acts as a decongestant via alpha-adrenergic receptor agonism in the respiratory tract mucosa, causing vasoconstriction and reduced edema.
| Metabolism | Cetirizine undergoes minimal hepatic metabolism (oxidative O-dealkylation) primarily via CYP3A4, with negligible contribution from other CYP enzymes. Pseudoephedrine undergoes partial hepatic metabolism (N-demethylation) and is excreted largely unchanged in urine (70-90%). |
| Excretion | Cetirizine: 70% renal (unchanged), 10% fecal. Pseudoephedrine: 90% renal (unchanged), remainder metabolized and excreted in urine. |
| Half-life | Cetirizine: 8-10 hours in healthy adults; increased in renal impairment (e.g., up to 30 hours in severe impairment). Pseudoephedrine: 5-8 hours (pH-dependent; longer in alkaline urine). |
| Protein binding | Cetirizine: 93% bound (albumin). Pseudoephedrine: negligible (<5%). |
| Volume of Distribution | Cetirizine: 0.3-0.5 L/kg; distributes into extracellular fluid. Pseudoephedrine: 2.6-3.0 L/kg; extensive tissue distribution. |
| Bioavailability | Cetirizine: 70% (oral). Pseudoephedrine: 100% (oral); first-pass metabolism minimal. |
| Onset of Action | Cetirizine: 1 hour (oral). Pseudoephedrine: 15-30 minutes (oral). |
| Duration of Action | Cetirizine: 24 hours. Pseudoephedrine: 4-6 hours (immediate-release); 12-hour formulation provides extended decongestant effect. |
1 tablet (5 mg cetirizine / 120 mg pseudoephedrine) orally every 12 hours. Maximum 2 tablets per 24 hours.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | Creatinine clearance 30-49 mL/min: 1 tablet every 24 hours. Creatinine clearance <30 mL/min or ESRD: contraindicated. |
| Liver impairment | Child-Pugh class A: no adjustment. Child-Pugh class B: 1 tablet every 24 hours. Child-Pugh class C: not recommended. |
| Pediatric use | Not recommended for children under 12 years of age. For children ≥12 years: same as adult. |
| Geriatric use | Initiate at 1 tablet every 24 hours due to increased sensitivity and renal function decline. Monitor for anticholinergic effects and cardiovascular adverse events. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZYRTEC-D 12 HOUR (ZYRTEC-D 12 HOUR).
| Breastfeeding | Cetirizine: Excreted into breast milk (M/P ratio ≈ 0.25-0.5); low risk. Pseudoephedrine: Excreted into breast milk (M/P ratio ≈ 2.6-3.5); may cause infant irritability; avoid if possible. |
| Teratogenic Risk | Cetirizine (pseudoephedrine): First trimester: Limited human data, animal studies show no teratogenicity, but pseudoephedrine is a vasoconstrictor; risk of fetal hypoxia. Second/third trimester: Pseudoephedrine may cause uterine artery vasoconstriction, reducing placental perfusion; avoid near term due to risk of neonatal irritability. |
■ FDA Black Box Warning
None.
| Common Effects | Sleepiness Fatigue Vomiting Dryness in mouth Headache Constipation |
| Serious Effects |
["Severe hypertension","Coronary artery disease","Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuation","Narrow-angle glaucoma","Urinary retention","Severe renal impairment (CrCl <10 mL/min) for cetirizine component","Hypersensitivity to any component"]
| Precautions | ["Cardiovascular effects: hypertension, palpitations, tachycardia, arrhythmias (especially in patients with pre-existing cardiovascular disease)","CNS stimulation: insomnia, nervousness, dizziness, tremor; avoid use with other sympathomimetics","Urinary retention: caution in patients with prostatic hypertrophy or bladder neck obstruction","Increased intraocular pressure: avoid in narrow-angle glaucoma","Severe hepatic impairment: use with caution; dose adjustment may be necessary","Elderly patients: more sensitive to CNS and cardiovascular effects"] |
Loading safety data…
| Fetal Monitoring |
| Monitor maternal blood pressure (pseudoephedrine can cause hypertension), fetal heart rate (especially with maternal hypertension), and signs of uterine irritability. Consider Doppler studies if pseudoephedrine used in third trimester. |
| Fertility Effects | No known adverse effects on fertility from cetirizine or pseudoephedrine. Pseudoephedrine may transiently affect uterine contractility but no evidence of impaired fertility. |