Valganciclovir Side Effects
The most significant side effect of valganciclovir is myelosuppression, manifesting as neutropenia, anemia, and thrombocytopenia, which may require dose reduction or interruption in up to 40% of patients. 1, 2
Hematologic Toxicity (Most Critical)
Bone marrow suppression is the primary concern and requires vigilant monitoring:
- Neutropenia (ANC <500/μL) occurs in approximately 19% of patients during maintenance therapy 2
- Anemia (hemoglobin <8 g/dL) develops in 13-20% of patients 2
- Thrombocytopenia (platelets <50,000/μL) affects approximately 10% of patients 2
- Severe and potentially fatal bone marrow failure can occur, particularly with overdosing in renal impairment 3
- Regular complete blood count monitoring is essential, as dose reduction or temporary discontinuation may be necessary 1, 4
Critical pitfall: Standard 900 mg daily dosing without renal adjustment can cause severe, potentially fatal bone marrow depression within 18-20 days in patients with renal impairment 3
Gastrointestinal Side Effects
GI symptoms are the most common adverse events overall:
- Diarrhea occurs in 16-41% of patients 2, 5
- Nausea affects 8-30% of patients 2, 5
- Vomiting occurs in 21% of patients 2, 5
- Abdominal pain develops in 15% of patients 2
These symptoms are generally mild to moderate in intensity 2
Neurologic Side Effects
CNS effects can impair daily functioning and require specific precautions:
- Headache occurs in 9-22% of patients 2, 5
- Tremor is common, particularly in transplant recipients 2
- Insomnia affects 16% of patients 2, 5
- Peripheral neuropathy develops in 9% of patients 2, 5
- Paresthesias occur in 8% of patients 2, 5
- Seizures, sleepiness, dizziness, unsteady movements, and confusion can occur 2
Important caveat: Patients should not drive or operate dangerous machinery until they know how valganciclovir affects them 2
Renal Toxicity
Acute renal failure is a serious but less common complication:
- Elderly patients are at particular risk, even without preexisting renal impairment 2
- Patients receiving concurrent nephrotoxic drugs require caution 2
- Adequate hydration must be maintained for all patients 2
- Serum creatinine >2.5 mg/dL occurs in 3% of patients 2
- Dose adjustment is mandatory in renal impairment to prevent severe toxicity 4, 3
Reproductive and Developmental Toxicity
Valganciclovir poses significant risks to fertility and fetal development:
- May cause temporary or permanent inhibition of spermatogenesis in males 2
- May suppress fertility in females 2
- Potential for birth defects based on animal studies showing malformations in multiple organs 2
- Females of reproductive potential must use effective contraception during treatment and for at least 30 days after completion 2
- Males must practice barrier contraception during and for at least 90 days following treatment 2
Other Notable Side Effects
Additional adverse events occurring in ≥5% of patients include:
- Fever (pyrexia) in 31% of patients 2
- Retinal detachment in 15% of CMV retinitis patients (related to underlying disease) 2
- Graft rejection in transplant recipients 2
- Catheter-related infections (3% with oral valganciclovir vs 11% with IV ganciclovir) 2
Pediatric-Specific Considerations
Children experience similar adverse events with some differences in frequency:
- Hypertension is more commonly reported in pediatric transplant recipients 2
- Upper respiratory tract infections occur frequently 2
- Urinary tract infections are common 2
- Leukopenia may be more prominent than in adults 2
Monitoring Requirements to Mitigate Toxicity
Essential monitoring includes:
- Weekly complete blood counts during induction therapy 4
- Regular renal function monitoring 1, 4
- For CMV retinitis patients, regular ophthalmologic examinations 1, 4
- Increased monitoring when switching from oral ganciclovir to valganciclovir due to higher plasma concentrations 2
Carcinogenic and Mutagenic Potential
Long-term risks based on animal data: