Zeffix

Zeffix is an oral solution. It is a systemic drug with antiviral properties.

Indications Zeffix

Indicated for chronic hepatitis (viral) type B, which develops simultaneously with the replication of HBV.

Release form

It is produced as a solution in polyethylene bottles (with a screw cap) of 240 ml. One package contains 1 bottle complete with a polypropylene (or polyethylene) dosing syringe, as well as a polyethylene adapter for the syringe.

Pharmacodynamics

The active component of the drug, lamivudine, is an antiviral agent with high activity against hepatitis type B.

Lamivudine triphosphate is the active form of the substance – it is a substrate for the viral polymerase. Subsequent formation of viral DNA is blocked by the entry of the medicinal component into this chain. Lamivudine triphosphate does not interfere with the natural cellular metabolism of DNA.

Pharmacokinetics

The active ingredient has a high absorption rate from the gastrointestinal tract, and the level of bioavailability after internal administration is 80-85%. The peak serum concentration is observed 1 hour after use. When the drug is taken with food, the peak serum concentration decreases to 47%, and the time it takes to reach it is extended. But in general, this does not affect the absorbed substance, which allows you to use Zeffix regardless of food.

When distributed in medicinal doses, the drug's indices will be linear. The drug is poorly synthesized with plasma protein. There is limited information that lamivudine is able to pass into the CNS and cerebrospinal fluid. The average ratio of the substance in the blood serum and cerebrospinal fluid after 2-4 hours after oral administration is about 0.12.

Metabolic interaction of the substance is unlikely to be possible, since the substance has a rather low level of metabolism in the liver (only 5-10%), as well as weak synthesis with plasma protein.

The mean systemic clearance rate of lamivudine is approximately 0.3 L/h/kg, with a half-life of approximately 5-7 hours. The major portion of the active component is excreted unchanged in the urine by active secretion and glomerular filtration. Renal clearance is approximately 70% of the excreted lamivudine.

Dosing and administration

The medicine must be taken once a day, the daily dosage is 20 ml of solution. Taking the medicine does not depend on food intake. During the therapy, it is necessary to carefully monitor that the patient complies with the treatment regimen.

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Use Zeffix during pregnancy

There is enough information that the drug does not have a toxic effect on the pregnant woman's body and does not cause developmental defects. The drug is allowed to be used during pregnancy if there are clinical indications.

If pregnancy occurs during treatment with Zeffix, it is necessary to take into account that after stopping the use of the drug, the pathology may worsen.

Contraindications

Contraindications to the drug include patient intolerance to lamivudine or other components of the drug. In addition, it is not recommended to prescribe the drug to children under 18 years of age, since there is not enough information on the use of this drug in the above-mentioned age category.

Side effects Zeffix

The use of drugs can cause certain side effects, the most common of which are: infectious processes in the respiratory organs, rapid fatigue and a feeling of malaise, and in addition to this, also headaches, abdominal pain, diarrhea, vomiting, discomfort in the tonsils and throat, and along with this, nausea.

In addition, the development of such negative effects is also possible:

• digestive system organs: most often the ALT level increases, followed by an exacerbation of hepatitis (it can develop both during the course of treatment and after the drug is discontinued). Often the ALT level soon decreases, and in isolated cases it can be fatal;
• connective tissues, muscles and bone structure: muscle problems often develop (cramps, pain), and CPK levels also increase. Rhabdomyolysis occasionally appears;
• organs of the lymphatic and hematopoietic systems: thrombocytopenia develops occasionally;
• immune system: sometimes manifestations of hypersensitivity occur – Quincke's edema;
• Subcutaneous tissue and skin: itching and rashes often occur.

There have been cases of pancreatitis and nerve neuropathy (or paresthesia) in HIV patients, but it has not been possible to establish a clear link between treatment with Zeffix and the development of the above pathologies.

HIV-infected patients who took the drug in combination with nucleoside analogues sometimes developed lactic acidosis, usually accompanied by fatty liver and severe hepatomegaly.

Interactions with other drugs

Excretion of the drug occurs mainly through the kidneys (active secretion). Therefore, it is necessary to take into account that it can interact with drugs that have the same main excretion route (in this case, the procedure occurs with the participation of the organic cation transport system, for example with trimethoprim).

Combined use with trimethoprim or sulfamethoxazole in the amount of 160/800 mg increases the plasma levels of lamivudine by 40%. At the same time, Zeffix does not affect the pharmacokinetic properties of the above substances. But there is no need to adjust the dosage of the drug in case of normal kidney function.

The use of the drug together with zidovudine moderately increases the maximum values of the latter in plasma (28%), but AUC remains without significant changes. The pharmacokinetics of Zeffix under the influence of zidovudine does not change.

When combined with zalcitabine, Zeffix is able to inhibit the process of phosphorylation of this substance inside cells. In this regard, it is recommended not to use these drugs simultaneously. The same applies to the substance emtricitabine - due to the same effect of Zeffix on it, it is prohibited to combine these drugs.

The active substance of Zeffix in vitro helps intracellular reproduction of cladribine, which is why there is a risk of loss of effectiveness of the latter when used in combination. Some clinical data also confirm the possibility of interaction between these drugs. For this reason, their use in combination is not recommended.

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Storage conditions

The medicine must be kept in a place inaccessible to small children, under standard conditions. Temperature – no more than 25°C.

Shelf life

Zeffix is valid for use for 2 years from the date of manufacture of the medicine. But the shelf life after opening the bottle is only 1 month.