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) | 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.
Undesirable effects are described according to MedDRA System Organ Class and by estimated frequency based on post-marketing experience.
Frequencies are defined as follows:
Very common (≥1/10)
Common (≥1/100, <1/10)
Uncommon (≥1/1,000, <1/100)
Rare (≥1/10,000, <1/1,000)
Very rare (<1/10,000)
Not known (cannot be estimated from the available data).
Blood and lymphatic disorders:
Very rare: thrombocytopenia
Immune system disorders:
Rare: hypersensitivity
Very rare: anaphylactic shock
Metabolism and nutrition disorders:
Not known: increased appetite
Psychiatric disorders :
Uncommon : agitation
Rare : aggression, confusion, depression, hallucination, insomnia Very rare: tic
Not known: suicidal ideation, nightmares
Nervous system disorders:
Uncommon: paraesthesia
Rare: convulsions, movements disorders
Very rare: dysgeusia, syncope, tremor, dystonia, dyskinesia Not known: amnesia, memory impairment
Eye disorders:
Very rare: accommodation disorder, blurred vision, eye swelling, oculogyration
Not known: eye pain
Ear and labyrinth disorders:
Not known: vertigo
Cardiac disorders:
Rare: tachycardia
Respiratory, thoracic and mediastinal disorders:
Very rare: cough
Gastro-intestinal disorders:
Uncommon: diarrhoea Very rare: nausea
Hepatobiliary disorders:
Rare: hepatic function abnormal (increased transaminases, alkaline phosphatase, γ- GT and bilirubin)
Not known: Hepatitisa
a: Including Drug-induced liver injury (DILI) and other types of non-infectious hepatitis.
Skin and subcutaneous tissue disorders:
Uncommon: pruritus, rash Rare: urticaria
Very rare: angioneurotic oedema, fixed drug eruption
Not known: acute generalised exanthematous pustulosis (AGEP)
Musculoskeletal and connective tissue disorders:
Not known: arthralgia
Renal and urinary disorders:
Very rare: dysuria, enuresis
Not known: urinary retention
Reproductive system and breast disorders:
Not known: erectile dysfunction
General disorders and administration site conditions:
Uncommon: asthenia, malaise
Rare: oedema
Very rare: feeling abnormal
Not known: pruritus upon withdrawal
Investigations:
Rare: 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.