Adverse reactions are listed as follows by MedDRA body system organ class and by frequency.
The frequency categories used are: Very common ≥ 1 in 10, Common ≥ 1 in 100 and < 1 in 10, Uncommon ≥ 1 in 1,000 and < 1 in 100, Rare ≥ 1 in 10,000 and <1 in 1,000, Very rare < 1 in 10,000.
Clinical trial data have been used to assign frequency categories to adverse reactions if, in the trials, there was evidence of an association with valaciclovir (i.e. there was a statistically significant difference between the incidence in patients taking valaciclovir and placebo). For all other adverse events, spontaneous post-marketing data have been used as a basis for allocating frequency.
Clinical Trial Data: Nervous system disorders: Common: Headache.
Gastrointestinal disorders: Common: Nausea.
Post Marketing Data: Blood and lymphatic system disorders: Very rare: Leukopenia, thrombocytopenia.
Leukopenia is mainly reported in immunocompromised patients.
Immune system disorders: Very rare: Anaphylaxis.
Psychiatric and nervous system disorders: Rare: Dizziness, confusion, hallucinations, decreased consciousness. Very rare: Agitation, tremor, ataxia, dysarthria, psychotic symptoms, convulsions, encephalopathy, coma.
The above events are generally reversible and usually seen in patients with renal impairment or with other predisposing factors (see Precautions). In organ transplant patients receiving high doses (8g daily) of VALTREX for CMV prophylaxis, neurological reactions occurred more frequently compared with lower doses.
Respiratory, thoracic and mediastinal disorders: Uncommon: Dyspnoea.
Gastrointestinal disorders: Rare: Abdominal discomfort, vomiting, diarrhoea.
Hepato-biliary disorders: Very rare: Reversible increases in liver function tests.
These are occasionally described as hepatitis.
Skin and subcutaneous tissue disorders: Uncommon: Rashes including photosensitivity. Rare: Pruritus. Very rare: Urticaria, angioedema.
Renal and urinary disorders: Rare: Renal impairment. Very rare: Acute renal failure, renal pain.
Renal pain may be associated with renal failure.
Other: There have been reports of renal insufficiency, microangiopathic haemolytic anaemia and thrombocytopenia (sometimes in combination) in severely immunocompromised patients, particularly those with advanced HIV disease, receiving high doses (8 g daily) of valaciclovir for prolonged periods in clinical trials. These findings have been observed in patients not treated with valaciclovir who have the same underlying or concurrent conditions.