The active medical ingredient fosamprenavir is a so-called antiviral from the family of HIV protest inhibitors. It is used to treat HIV infections and is intended to prevent the development of AIDS (short for Acquired Immune Deficiency Syndrome). Fosamprenavir is marketed under the trade name Telzir and is manufactured by GlaxoSmithKline plc, based in London, UK.
What is fosamprenavir?
The drug fosamprenavir is a virostatic agent. This is a group of drugs that stops viruses from replicating. The drug belongs to the family of HIV protease inhibitors. These are active ingredients that specifically inhibit the activity of the protein-cleaving enzymes of the HIV virus. In addition to fosamprenavir, the preparations nelfinavir and lopinavir are also part of this group. By inhibiting protein cleavage, the replication of the HI virus is considerably slowed down. Fosamprenavir is used in tablet form and as a suspension. A suspension is a suspension of small particles that are placed in liquid but are not soluble. Medicines containing fosamprenavir are available by prescription throughout Europe. Independent use without a doctor’s prescription is prohibited. In Germany, therefore, there is also a pharmacy requirement.
Pharmacologic effect
As a virostatic agent fosamprenavir inhibits the reproduction of HIV in the human body. Unlike bacteria, viruses do not have an independent metabolism that could be interfered with by drugs. This makes the therapy of viruses fundamentally much more difficult. This is because the metabolism usually provides a readily accessible target for destroying a bacterium. The drug fosamprenavir therefore targets the protein cleavage of the HI viruses contained in the body. The cleavage of proteins (enzymes) is inhibited by fosamprenavir and similar drugs of the HIV protease inhibitors. As a result, no further infectious viruses are produced in the host cell of the body that has been attacked by the virus, since HI viruses depend on the enzyme they produce (protease) in order to be able to attack healthy blood cells (CD-4 cells). The degradation or excretion of fosamprenavir occurs primarily through the liver or stool. The half-life to complete excretion of the drug averages approximately 7 hours.
Medicinal use and application
Fosamprenavir is used exclusively in combination with other drugs as part of a comprehensive and fully medically supervised HIV therapy (combination therapy). An indication exists only for concomitant use of low-dose ritonavir or similar antiretroviral drugs. Ritonavir increases the drug level of fosamprenavir. The recommended daily amount of fosamprenavir is one film-coated tablet twice daily, each containing 700 mg of active ingredient. In addition to these two tablets, the other HIV preparations (e.g. 100 g ritonavir) should be taken. Thus, a patient takes a total of four tablets a day (two tablets of fosamprenavir and two tablets of ritonavir). Compared with treatments with the predecessor drug amprenavir, there is thus a considerable reduction in the number of tablets taken daily. Fosamprenavir is not used for preventive HIV treatment as part of so-called PrEP (pre-exposure prophylaxis). Its scope remains limited to HIV combination therapy.
Risks and side effects
It is mandatory that fosamprenavir be used together with low-dose ritonavir or other antiretroviral drugs. Only in this way can the intended purpose be effectively achieved. Each application must therefore be discussed with a doctor or pharmacist. The use of fosamprenavir is prohibited if hypersensitivity (allergy) to fosamprenavir, amprenavir or other components of HIV medications exists. Medicines containing fosamprenavir must not be taken with the following preparations:
- Astemizole or terfenadine (symptomatic treatment of allergies).
- Alfuzosin (treatment of prostate disease).
- Cisapride (treatment of digestive disorders).
- Pimozide (treatment of schizophrenia).
- Ergotamine derivatives (found in some headache tablets),
- Rifampicin (therapy of tuberculosis).
- Propafenone, quinidine, flecainide or amiodarone (preparations for the therapy of diseases of the heart).
- Sildenafil (treatment of erectile dysfunction and diseases of the pulmonary vessels).
- Preparations containing St. John’s wort.
Fosamprenavir may cause side effects. To date, the following side effects have been reported:
- Diarrhea
- Increases in blood cholesterol levels
- Increased_blood_fat levels
- General malaise and feelings of illness (also associated with nausea, vomiting and abdominal pain).
- Skin irritation (swelling, itching, redness.
- Headache
- Dizziness
- Fatigue
- Numbness or a tingling sensation in the mouth area.
- Increased transaminase and lipase levels
- Facial swelling (especially of the lips or tongue)
- Development of Stevens-Johnson syndrome. This is a severe skin reaction that can also assume life-threatening proportions.
