Valganciclovir

Valganciclovir is an antiviral medicine approved for treating and preventing disease caused by cytomegalovirus (CMV) — a common virus that can be dangerous in people with weakened immune systems.

• Treats CMV retinitis (a serious viral infection of the eye's retina) in adults with AIDS
• Prevents CMV disease in adult kidney transplant patients at high risk (those where the donor carried CMV antibodies but the recipient did not)
• Prevents CMV disease in adult heart transplant patients at high risk
• Prevents CMV disease in adult kidney-pancreas transplant patients at high risk
• Valganciclovir for oral solution prevents CMV disease in pediatric kidney transplant patients ages 4 months to 16 years at high risk
• Valganciclovir for oral solution and tablets prevent CMV disease in pediatric heart transplant patients ages 1 month to 16 years at high risk
• Valcyte (valganciclovir) tablets and oral solution carry full pediatric labeling including kidney transplant patients 4 months to 16 years and heart transplant patients 1 month to 16 years

Valganciclovir is a prodrug — your stomach and liver quickly convert it into its active form, ganciclovir. In cells infected with CMV, ganciclovir is transformed by a viral enzyme into a highly active molecule that blocks the virus's DNA polymerase (the enzyme CMV needs to copy its DNA). Because this activation step depends largely on the viral enzyme, it happens mainly inside infected cells, which helps focus the drug's effect where it's needed most. Without working DNA polymerase, the virus cannot replicate and spread.

Valganciclovir is taken by mouth and should always be taken with food — eating increases how much the drug your body absorbs. Adults treating CMV retinitis start with a twice-daily induction phase, then move to once-daily maintenance; transplant patients generally take it once daily, starting within 10 days of transplant and continuing for up to 100 or 200 days depending on the type of organ received. Pediatric doses are calculated individually based on the child's weight and kidney function.

• Always take with food
• Follow your prescriber's schedule exactly — do not skip doses or stop early without guidance
• The oral solution must be prepared by a pharmacist before dispensing and is the preferred form for young children
• Adults on hemodialysis cannot use the tablet form — discuss alternatives with your doctor

The most common side effects reported in adults and children taking valganciclovir include:

• Diarrhea
• Nausea and vomiting
• Fever
• Headache
• Tremor (shakiness)
• Fatigue
• Trouble sleeping
• Low white blood cell counts (neutropenia, leukopenia)
• Low red blood cell counts (anemia)
• Low platelet counts (thrombocytopenia)
• Urinary tract infections

Serious reactions that require immediate medical attention include severe drops in blood counts, bone marrow failure, acute kidney failure, seizures, and signs of serious infection. Contact your doctor right away if you notice unusual bruising, bleeding, extreme fatigue, or decreased urination.

• Blood and bone marrow toxicity: Valganciclovir can dangerously lower white blood cells, red blood cells, and platelets — and in rare cases cause complete bone marrow failure. Blood counts must be checked regularly. Treatment may need to stop if counts fall too low.
• Kidney failure: Acute kidney failure has occurred, especially in older adults, people not drinking enough fluids, and those taking other drugs that affect the kidneys. Stay hydrated and have kidney function monitored.
• Birth defects: Animal data show this drug can cause serious fetal malformations. Women must use effective contraception during treatment and for 30 days after; men must use condoms during and for 90 days after treatment.
• Fertility: Valganciclovir may temporarily or permanently reduce sperm production in men and suppress fertility in women.
• Cancer risk: Based on animal data, valganciclovir is considered a potential carcinogen (cancer-causing agent) in humans. Use only as prescribed.

Because valganciclovir converts to ganciclovir in the body, it shares ganciclovir's drug interactions. Key combinations to be aware of include:

• Imipenem-cilastatin: This antibiotic combination has caused seizures when used with ganciclovir — avoid using it together with valganciclovir unless absolutely necessary
• Cyclosporine or amphotericin B: Both can harm the kidneys; combining them with valganciclovir increases that risk — kidney function should be closely monitored
• Mycophenolate mofetil (MMF): Increases risk of blood toxicity and kidney problems; monitor carefully
• Didanosine (ddI): Valganciclovir raises didanosine blood levels, increasing the risk of pancreatitis (inflammation of the pancreas) and other side effects
• Probenecid: Raises ganciclovir levels in the blood; a dose reduction may be needed
• Other bone marrow-suppressing or kidney-toxic drugs (such as zidovudine, dapsone, hydroxyurea, tacrolimus, trimethoprim/sulfamethoxazole, vincristine, vinblastine, doxorubicin, flucytosine, pentamidine, adriamycin): Use together only when benefits clearly outweigh the risks

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Tell your doctor if you have kidney disease or are on dialysis — dosing must be adjusted, and adults on hemodialysis cannot use the tablet form at all
• Do not take valganciclovir if you have had a serious allergic reaction (such as anaphylaxis) to valganciclovir or ganciclovir in the past
• Women of childbearing potential must have a pregnancy test before starting and must use effective contraception during treatment and for at least 30 days after
• Men must use condoms during treatment and for at least 90 days after, due to the drug's mutagenic (DNA-damaging) potential
• Do not breastfeed while taking valganciclovir — it is not known whether the drug passes into human milk, and the potential risks to a nursing infant are serious
• Older adults should be monitored closely; kidney function naturally declines with age, which affects how the drug is cleared
• Tell your doctor if you have a history of low blood counts or are taking any drug that suppresses the immune system or bone marrow
• Inform your doctor of all medications you take, including transplant anti-rejection drugs, HIV medications, and antibiotics

Taking too much valganciclovir can seriously worsen blood toxicity (causing dangerously low blood counts including bone marrow failure), harm the kidneys, and in some cases cause seizures, liver problems, or severe gastrointestinal symptoms. Because ganciclovir (the active form) can be partially removed by dialysis, dialysis may help lower blood levels after an overdose. The label also recommends maintaining good hydration and considering the use of blood-cell-stimulating growth factors if blood counts fall dangerously low — these decisions should be made by a healthcare team.

Valganciclovir works by being converted to ganciclovir, which is then activated inside CMV-infected cells into a molecule that specifically blocks the viral DNA polymerase. This stops CMV from replicating its genetic material and producing new virus particles. Because the key activation step relies on a viral enzyme found mainly in infected cells, the drug's effects are directed preferentially at those cells rather than healthy ones.

After you swallow valganciclovir, it is rapidly converted by enzymes in your gut and liver into ganciclovir — the active drug. Taking it with food significantly increases how much ganciclovir reaches your bloodstream (by about 30%). Ganciclovir is eliminated almost entirely by the kidneys through a combination of filtration and active secretion, so people with reduced kidney function clear the drug much more slowly and need lower doses. Hemodialysis removes about half of the ganciclovir from the blood, which is important to know in cases of overdose or dose management.

Store VALCYTE tablets at 20°C to 25°C (68°F to 77°F); excursions are permitted to 15°C to 30°C (59°F to 86°F) . Store dry powder at 20°C to 25°C (68°F to 77°F); excursions are permitted to 15°C to 30°C (59°F to 86°F) .