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 dihydrochloride.
Clinical trials
Double blind controlled clinical trials comparing cetirizine to placebo or other antihistamines at the recommended dosage (10 mg 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 10 mg in the placebo controlled trials at rates of 1.0 % or greater:
| Adverse event (WHO-ART) | Cetirizine 10 mg (n = 3260) | Placebo (n = 3061) |
| Body as a whole – general disorders Fatigue | 1,63 % | 0,95 % |
| Central and peripheral nervous system disorders Dizziness Headache | 1,10 % 7,42 % | 0,98 % 8,07 % |
| Gastro-intestinal system disorders Abdominal pain Dry mouth Nausea | 0,98 % 2,09 % 1,07 % | 1,08 % 0,82 % 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 trials are:
| Adverse drug reactions (WHO-ART) | Cetirizin 10 mg (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 reactions reported during clinical studies and listed above, the following undesirable effects have been reported in postmarketing experience.
Undesirable effects are described according to MEDdra System Order Class and by estimated frequency, based on post-marketing experience.
Frequencies are defined as follows: Very common (≥ 1/10); common (≥ 1/100 to <1/10); 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).
| System organ class | Common | Uncommon | Rare | Very rare | Not Known |
| Blood and lymphatic disorders: | | | | Thrombocytopenia | |
| Immune system disorders: | | | Hypersensitivity | Anaphylactic shock | |
| Metabolism and nutrition disorders: | | | | | Increased appetite |
| Psychiatric disorders: | | Agitation | Aggression, confusion, depression, hallucination, insomnia | Tics | Suicidal ideation |
| Nervous system disorders: | | Paraesthesia | Convulsions | Dysgeusia, dystonia, dyskinesia, syncope, tremor | Amnesia, memory impairment |
| Eye disorders: | | | | Accommodation disorder, vision blurred, oculogyration | Eye pain |
| Ear and labyrinth disorders: | | | | | Vertigo |
| Cardiac disorders: | | | Tachycardia | | |
| Gastro-intestinal disorders: | | Diarrhoea | | | |
| Hepatobiliary disorders: | | | Hepatic function abnormal (increased transaminases, alkaline phosphatase, γ-GT and bilirubin) | | Hepatitis |
| Skin and subcutaneous tissue disorders: | | Pruritus, rash | Urticaria | Angioneurotic oedema, fixed drug eruption | Acute generalised exanthematous pustulosis (AGEP) |
| Musculoskeletal and connective tissue disorders: | | | | | Arthralgia |
| Renal and urinary disorders: | | | | Dysuria, enuresis | Urinary retention |
| Reproductive system and breast disorders: | | | | | Erectile dysfunction |
| General disorders and administration site conditions: | | Asthenia, malaise | Oedema | | Pruritus on withdrawal |
| Investigations: | | | Weight increased | | |
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.