Videx

Videx is an antiviral drug with a direct type of therapeutic effect. [ 1 ]

Didanosine inhibits HIV replication in vitro in cultured human cells and cell lines. Once inside the cell, the element is enzymatically converted to its metabolic component, dideoxyadenosine-3-phosphate. During viral replication of nucleic acid, the use of 2b3'-dideoxynucleoside prevents chain prolongation, thereby slowing the replication process. In addition, ddATP slows the action of HIV reverse transcriptase, disrupting the binding of proviral DNA. [ 2 ]

Indications Videx

It is used in HIV infection (in combination with other antiretroviral agents). [ 3 ]

Release form

The drug is released in capsules - 10 pieces inside a blister pack; inside a pack - 3 such packs.

Pharmacokinetics

It takes approximately 120 minutes for didanosine to reach plasma Cmax values; the Cmax value itself is directly dependent on the dose size of the drug taken.

The average level of didanosine in the cerebrospinal fluid is equal to 21% of the simultaneously recorded plasma values of the substance.

The capsules are taken on an empty stomach, since their administration with food reduces the Cmax values by 46% and the AUC level by 19%.

In humans, the metabolic processes of didanosine have been studied rather poorly. Based on experimental data, it is believed that in humans they are realized through the metabolism of internal purines.

When administered orally, the half-life is on average 1.6 hours (for tablets), but because the absorption rate of the substance from capsules is much lower, its half-life in this case will be approximately 50% longer. Excretion of the drug in the urine is approximately 20% of the orally administered portion.

The intrarenal clearance rate is 50% of its total values (0.8 l per minute) – this confirms the active processes of CF and secretion through the tubules during renal excretion of didanosine. After 1-month oral administration of the drug, didanosine did not accumulate in the body.

Use in persons with renal dysfunction.

When administered orally, the half-life is increased by an average of at least 1.4 hours (in the case of normal renal function) and a maximum of 4.1 hours (if severe dysfunction is observed). The drug is not registered in the dialysis peritoneal fluid, but during hemodialysis, after 3-4 hours, the plasma level of didanosine was within 0.6-7.4% of the dose taken.

In case of renal dysfunction (CC values below 60 ml per minute/1.73 m2), the dose of the drug is selected individually.

Use in people with liver dysfunction.

The metabolic processes of didanosine are determined by the severity of liver dysfunction, which may require a reduction in the dosage of Videx.

Dosing and administration

The medicine is taken 1-2 times a day. The capsules are swallowed whole, without chewing. They should be taken on an empty stomach (or half an hour before or 2 hours after a meal), washed down with at least 0.1 liters of plain water (to improve absorption of the drug). Capsules must not be opened, because this can reduce their medicinal effect.

The daily portion size is determined by the patient's weight:

• weight >60 kg – 0.4 g, 1 time per day;
• weight <60 kg – 0.25 g, 1 time per day.

No special studies have been conducted on the administration of capsules in pediatrics, but when using other forms of the drug, the required daily dosage (calculated based on body surface area) was 0.24 g/m2 (0.18 g/m2 when combined with zidovudine).

For adults with renal dysfunction, the dosage should be reduced or the interval between Videx administrations should be extended (taking into account the CC values).

Weight >60 kg:

• the level of CC is >60 ml per minute/1.73 m2 – 0.4 g per day;
• in the range of 30-59 ml per minute/1.73 m2 – 0.25 g per day;
• within 10-29 ml per minute/1.73 m2 – a different form of drug release is used.
• Weight <60 kg:
• CC values are >60 ml per minute/1.73 m2 – 0.25 g per day;
• indicators within the range of 30-59 ml per minute/1.73 m2 – the medicine is administered in a different form of release.

People undergoing hemodialysis should consume the daily dose after the procedure. No additional dosage is required.

Elderly people.

Before using the drug, it is necessary to check renal function, because this group has a high risk of renal failure, which requires the use of a personally selected dosage.

Persons with liver dysfunction.

A reduction in the dose of the drug is required, but there are no specific indications for changing the dosage. During therapy, it is necessary to monitor the values of liver enzymes. If a clinically significant increase in their values is noted, the therapy is stopped. A rapid increase in aminotransferase values may require complete cancellation of therapy with the introduction of any nucleoside analogues.

Missed dose of medication.

If you accidentally miss the time for taking the medication, continue taking the usual dosage (doubling the dose to compensate for the previously missed dose is prohibited).

• Application for children

In pediatrics, the drug is used in a different form.

Use Videx during pregnancy

In animal studies, didanosine did not exhibit fetotoxic or embryotoxic or teratogenic effects.

Pregnant women are prescribed the drug only under strict indications and in situations where the benefit of therapy is more likely than the risk of negative consequences for the fetus.

Women with HIV infection should not breastfeed because this can lead to infection of the baby.

Contraindications

Contraindication is severe intolerance to didanosine or other components of the drug.

Side effects Videx

When treating HIV-infected patients, it is extremely difficult to distinguish between negative manifestations associated with taking Videx and the negative effect of other drugs used in combination, as well as negative symptoms associated with the disease itself. Among the side effects encountered:

• dysfunction of the nervous system: neurological manifestations of a peripheral type (including neuropathy) often occur, as well as headaches;
• digestive problems: diarrhea is the most common. Bloating, nausea, xerostomia, abdominal pain, vomiting, liver failure and hepatitis are also quite common;
• lesions of the subcutaneous layers with the epidermis: rashes often appear;
• systemic disorders: asthenia or fatigue;
• metabolic disorders: diabetes, hyper- or hypoglycemia, and lactic acidosis;
• problems with the visual organs: retinal depigmentation, dry eye mucosa and neuritis affecting the optic nerve;
• immune disorders: anaphylactic symptoms;
• infections: sialoadenitis;
• other signs: chills, arthralgia, alopecia, anemia, anaphylactoid manifestations, anorexia and myalgia, as well as inflammation affecting the salivary glands, rhabdomyolysis, thrombocytopenia or leukopenia, myopathy, hyperbilirubinemia and increased blood lactic acid levels;
• changes in test results: increase in serum values of alkaline phosphatase, ALT with AST, lipase and amylase.

Overdose

Clinical symptoms of overdose include hyperuricemia, pancreatitis, liver dysfunction, polyneuropathy, and diarrhea.

In case of accidental use of a dose exceeding the daily dose, gastric lavage with water and administration of activated carbon are performed. There is no antidote for didanosine. In cases of significant poisoning, liver dysfunction and hyperuricemia have been observed. In such disorders, hemodialysis is performed (a 3-4 hour session leads to a decrease in didanosine levels by 20-30%), and in addition, symptomatic measures are taken.

Interactions with other drugs

Combined systematic use of the drug with ganciclovir (or taking didanosine 2 hours before ganciclovir) leads to a prolongation of the residence time of didanosine in the blood plasma by up to 111% on average.

Combination of Videx with itraconazole or ketoconazole prolonged the intraplasmic residence time of didanosine and its parameters by 30%.

Use of the drug together with substances capable of causing pancreatitis or polyneuropathy may increase the likelihood of developing the described toxic symptoms. Patients using such drug combinations should be closely monitored.

Administration of the drug in combination with tenofovir increases the systemic excretion of the former and its average levels in urine.

Storage conditions

Videx should be stored in a place closed to small children. Temperature values should not exceed 25°C.

Shelf life

Videx can be used within a 24-month period from the date of manufacture of the drug.

Analogues

Analogues of the drug are Fadinosine and Didanosine.