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Prior to the initiation of valganciclovir treatment, patients should be advised of the potential risks to the foetus. In animal studies, ganciclovir was found to be mutagenic, teratogenic, aspermatogenic and carcinogenic, and a suppressor of female fertility. Valganciclovir should, therefore, be considered a potential teratogen and carcinogen in humans with the potential to cause birth defects and cancers. It is also considered likely that Valganciclovir causes temporary or permanent inhibition of spermatogenesis. Women of child bearing potential must be advised to use effective contraception during treatment. Men must be advised to practise barrier contraception during treatment, and for at least 90 days thereafter, unless it is certain that the female partner is not at risk of pregnancy.
Valganciclovir has the potential to cause carcinogenicity and reproductive toxicity in the long term.
Severe leucopenia, neutropenia, anaemia, thrombocytopenia, pancytopenia, bone marrow depression and aplastic anaemia have been observed in patients treated with Valganciclovir (and ganciclovir). Therapy should not be initiated if the absolute neutrophil count is less than 500 cells/μl, or the platelet count is less than 25000/μl, or the haemoglobin level is less than 8 g/dl.
When extending prophylaxis beyond 100 days the possible risk of developing leucopenia and neutropenia should be taken into account.
Valganciclovir should be used with caution in patients with pre-existing haematological cytopenia or a history of drug-related haematological cytopenia and in patients receiving radiotherapy.
It is recommended that complete blood counts and platelet counts should be monitored regularly during therapy, especially in patients in whom ganciclovir or other nucleoside analogues have previously resulted in leukopenia, or in whom neutrophil counts are less than 1000 cell/μl at the beginning of the treatment and in neonates and infants.
Increased haematological monitoring may be warranted in patients with renal impairment at a minimum each time the patient attends the transplant clinic. In patients developing severe leucopenia, neutropenia, anaemia and/or thrombocytopenia, it is recommended that treatment with haematopoietic growth factors and/or dose interruption be considered.
The bioavailability of ganciclovir after a single dose of 900 mg valganciclovir is approximately 60%, compared with approximately 6% after administration of 1000 mg oral ganciclovir (as capsules). Excessive exposure to ganciclovir may be associated with life-threatening adverse reactions. Therefore, careful adherence to the dose recommendations is advised when instituting therapy, when switching from induction to maintenance therapy and in patients who may switch from oral ganciclovir to valganciclovir as Valganciclovir cannot be substituted for ganciclovir capsules on a one-to-one basis. Patients switching from ganciclovir capsules should be advised of the risk of over dosage if they take more than the prescribed number of Valganciclovir tablets.
In patients with impaired renal function, dosage adjustments based on creatinine clearance are required.
Valganciclovir film-coated tablets should not be used in patients on haemodialysis.
Convulsions have been reported in patients taking imipenem-cilastatin and ganciclovir. Valganciclovir should not be used concomitantly with imipenem-cilastatin unless the potential benefits outweigh the potential risks.
Patients treated with Valganciclovir and (a) didanosine, (b) drugs that are known to be myelosuppressive (e.g. zidovudine), or (c) substances affecting renal function, should be closely monitored for signs of added toxicity.
The controlled clinical study using valganciclovir for the prophylactic treatment of CMV disease in transplantation, as detailed in pharmacodynamic properties, did not include lung and intestinal transplant patients. Therefore, experience in these transplant patients is limited.
The diagnosis of CMV retinitis should be made by indirect opthalmoscopy. Other conditions in the differential diagnosis of CMV retinitis include candidiasis, toxoplasmosis, histoplasmosis, retinal scars and cotton wool spots, any of which may produce a retinal appearance similar to CMV. For this reason it is essential that the diagnosis of CMV be established by an ophthalmologist familiar with the presentation of these conditions. The diagnosis of CMV retinitis may be supported by culture of CMV in the urine, blood throat, or other sites, but a negative culture does not rule out CMV retinitis.
Effects on ability to drive and use machines: No studies on the effects on ability to drive and use machines have been performed.
Convulsions, sedation, dizziness, ataxia, and/or confusion have been reported with the use of Valganciclovir and/or ganciclovir. If they occur, such effects may affect tasks requiring alertness, including the patient's ability to drive and operate machinery.
