| Clinical studies have shown that cetirizine at the recommended dosage has minor undesirable effects on the CNS, including somnolence, fatigue, dizziness and headache. In some cases, paradoxical CNS stimulation has been reported.Although cetirizine is a selective antagonist of peripheral H1-receptors and is relatively free of anticholinergic activity, isolated cases of micturition difficulty, eye accommodation disorders and dry mouth have been reported.Instances of abnormal hepatic function with elevated hepatic enzymes accompanied by elevated bilirubin have been reported. Mostly this resolves upon discontinuation of the treatment with cetirizine hydrochloride. Clinical trials: Double blind controlled clinical or pharmacoclinical trials comparing cetirizine to placebo or other antihistamines at the recommended dosage (10mg daily for cetirizine), of which quantified safety data are available, included more than 3200 subjects exposed to cetirizine.From this pooling, the following adverse events were reported for cetirizine 10mg in the placebo-controlled trials at rates of 1.0% or greater:Adverse event (WHO-ART) | Cetirizine 10mg (n= 3260) | Placebo (n= 3061) | Body as a whole- general disorders | Fatigue | 1.63% | 0.95% | Central and peripheral nervous system disorders | Dizziness | 1.10% | 0.98% | Headache | 7.42% | 8.07% | Gastro-intestinal system disorders | Abdominal pain | 0.98% | 1.08% | Dry mouth | 2.09% | 0.82% | Nausea | 1.07% | 1.14% | Psychiatric disorders | Somnolence | 9.63% | 5.00% | Respiratory system disorders | Pharyngitis | 1.29% | 1.34% | Although statistically more common than under placebo, somnolence was mild to moderate in the majority of cases. Objective tests as demonstrated by other studies have demonstrated that usual daily activities are unaffected at the recommended daily dose in healthy young volunteers.Adverse drug reactions at rates of 1% or greater in children aged from 6 months to 12 years, included in placebo-controlled clinical or pharmacological trials are:Adverse event (WHO-ART) | Cetirizine (n= 1656) | Placebo (n= 1294) | Gastro-intestinal system disorders | Diarrhoea | 1.0% | 0.6% | Psychiatric disorders | Somnolence | 1.8% | 1.4% | Respiratory system disorders | Rhinitis | 1.4% | 1.1% | Body as a whole- general disorders | Fatigue | 1.0% | 0.3% |
Post-marketing experience In addition to the adverse effects reported during clinical studies and listed above, isolated cases of the following adverse drug reactions have been reported in post-marketing experience. For these less frequently reported undesirable effects, the estimated frequencies (uncommon: 1/1,000 to <1/100, rare: 1/10,000 to <1/1,000), very rare: <1/10,000), not known (cannot be estimated from the available data) are made based on post-marketing experience.Investigations: Rare: weight increasedCardiac disorders: Rare: tachycardiaBlood and lymphatic disorders: Very rare: thrombocytopeniaNervous system disorders: Uncommon: paraesthesiaRare: convulsions, movement disordersVery rare: dysgeusia, syncope, tremor, dystonia, dyskinesiaNot known: amnesia, memory impairmentEye disorders: Very rare: accommodation disorder, blurred vision, oculogyrationGastrointestinal disorders: Uncommon: diarrhoea Renal and urinary disorders: Very rare: dysuria, enuresisSkin and subcutaneous tissue disorders: Uncommon: pruritus, rashRare: urticaria.Very rare: angioneurotic oedema, fixed drug eruptionGeneral disorders and administration site conditions: Uncommon: asthenia, malaiseRare: oedemaImmune system disorders Rare: hypersensitivityVery rare: anaphylactic shockHepato-billiary disorders: Rare: hepatic function abnormal (increased transaminases, alkaline phosphatase, γ-GT and bilirubin)Psychiatric disorders: Uncommon: agitationRare: aggression, confusion, depression, hallucination, insomniaVery rare: tics
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