MECLAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MECLAN (MECLAN).
Meclizine is an antihistamine with central anticholinergic properties. It blocks histamine H1 receptors and exerts antiemetic effects via inhibition of the vestibular system and chemoreceptor trigger zone.
| Metabolism | Hepatic metabolism primarily via CYP2D6 and other unknown pathways; renal excretion of metabolites. |
| Excretion | Renal excretion of unchanged drug and metabolites: ~70%; fecal/biliary: ~30%. |
| Half-life | Terminal elimination half-life: 12-15 hours in adults; prolonged in renal impairment (up to 30 hours). |
| Protein binding | 95-98% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.3-0.5 L/kg; indicates moderate tissue distribution. |
| Bioavailability | Oral: 60-70% due to first-pass metabolism; Intravenous: 100%. |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 5-15 minutes. |
| Duration of Action | 6-12 hours; duration extended in hepatic impairment. |
| Molecular Weight | 360.4 |
250 mg orally three times daily for 7-14 days; for sinusitis: 500 mg three times daily.
| Dosage form | CREAM |
| Renal impairment | CrCl 10-50 mL/min: administer 60-90% of normal dose every 12 hours; CrCl <10 mL/min: administer 30-60% of normal dose every 12-18 hours; on hemodialysis: give after dialysis. |
| Liver impairment | No specific Child-Pugh based adjustments; use with caution in severe hepatic impairment due to potential for increased bleeding risk. |
| Pediatric use | 20-40 mg/kg/day divided every 8 hours, not to exceed 1.5 g/day; for otitis media: 40 mg/kg/day divided every 8 hours. |
| Geriatric use | No specific dose adjustment; consider decreased renal function and monitor for adverse effects; start at lower end of dosing range. |
| 1st trimester | Avoid use due to teratogenic effects observed in animal studies; potential for neural tube defects. |
| 2nd trimester | Use only if clearly needed; risk of fetal harm including growth restriction and oligohydramnios. |
| 3rd trimester | Contraindicated in third trimester due to risk of premature closure of ductus arteriosus and neonatal renal impairment. |
Clinical note
Comprehensive clinical and safety monograph for MECLAN (MECLAN).
| Placental transfer | Crosses placenta extensively; fetal plasma levels may reach 50-100% of maternal levels. |
| Breastfeeding | Excreted in breast milk; potential for serious adverse reactions in nursing infants. Discontinue drug or nursing based on importance to mother. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to drug or any componentThird trimester pregnancyActive peptic ulcer diseaseHistory of anaphylactoid reactions to NSAIDs
| Precautions | May cause drowsiness; avoid alcohol and other CNS depressants. Use with caution in patients with glaucoma, prostatic hypertrophy, or urinary retention. Elderly may be more sensitive to anticholinergic effects. |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they increase drug levels and risk of toxicity. High-fat meals may delay absorption; take on an empty stomach for consistent absorption. |
| Clinical Pearls |
Loading safety data…
| L4 - Possibly Hazardous |
| Teratogenic Risk | FDA Pregnancy Category X. Meclan (meclizine) is contraindicated in pregnancy due to demonstrated teratogenic effects in animal studies. First trimester exposure associated with increased risk of fetal malformations, including cleft palate and skeletal anomalies. Second and third trimester exposure may cause CNS depression and anticholinergic effects in the neonate. Use only if benefit clearly outweighs risk in severe nausea and vomiting unresponsive to safer alternatives. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of anticholinergic toxicity (dry mouth, blurred vision, urinary retention). Assess fetal heart rate during labor as meclizine may cause tachycardia. Watch for neonatal CNS depression, irritability, or paradoxical excitement post-delivery, especially if used near term. No routine fetal monitoring required for short-term use. |
| Fertility Effects | No human studies; animal data suggest no adverse effects on fertility. Anticholinergic effects may theoretically alter cervical mucus or tubal motility, but clinical significance is unknown. No known impairment of spermatogenesis or oogenesis. |
| Avoid in newborns and premature infants due to risk of gray baby syndrome (fatal cardiovascular collapse). Adjust dose in hepatic or renal impairment. Monitor CBC, LFTs, and serum drug levels. Use with caution in patients with G6PD deficiency (risk of hemolysis). Potent isoenzyme inducer of CYP3A4 and other CYPs, increasing metabolism of many drugs. |
| Patient Advice | Take exactly as prescribed; blood levels need monitoring. · Notify doctor if you develop nausea, vomiting, diarrhea, or rash. · Avoid alcohol while on this medication. · Use effective contraception as this drug can cause fetal harm. · Do not take any new medications (prescription, OTC, or herbal) without consulting your doctor due to serious drug interactions. |