Amprenavir is a medical agent and belongs to the group of HIV protease inhibitors. The drug is used to treat HIV infection.
What is amprenavir?
Amprenavir is a medical agent and belongs to the group of HIV protease inhibitors. The drug is used to treat HIV infection. Amprenavir is a drug marketed in Germany, Austria, and Switzerland under the name Agenerase. The drug is a protease inhibitor. Its development took place in the early 1990s by the company Vertex Pharmaceuticals. Amprenavir has been marketed as an antiviral agent since 1995. It was approved by the EMA (European Medicines Agency) in 2000. Around 90 percent of amprenavir is bound to proteins in the blood. The active ingredient is broken down in the liver by the cytochrome system. If the patient takes amprenavir together with another protease inhibitor, this process can be slowed down. In this way, the duration of action of the drug lasts longer. The half-life is estimated to be about 10 hours. In addition, nucleoside reverse transcriptase inhibitors (NRTIs) can be administered at the same time.
Pharmacologic effect
The principle of action of amprenavir is inhibition of viral replication. Thus, viral protease of the enzyme HIV protease is counteracted. HIV protease is of paramount importance for the generation of further viral particles with infectious activity. However, if the protease can be inhibited, the spread of the viruses in the human organism can be reduced. By reducing further multiplication of the viruses, the viral load eventually decreases. The basis of the effect is the prevention of the cleavage of viral precursor proteins. This results in the formation of immature viral particles that are not infectious. In contrast to older active substances of this type, the binding mechanism between the active substance and the enzyme is different. Thus, cross-resistance to amprenavir does not occur in patients who react negatively to older protease inhibitors. During the clinical trial, a comparison was made between amprenavir and the established HIV protease inhibitor indinavir. The efficacy of amprenavir was lower than that of indinavir.
Medical Application and Use
Amprenavir, like all other HIV protease inhibitors, is used to treat HIV infections such as AIDS. In treatment, the drug is combined with other antivirals. Amprenavir is suitable for the treatment of both adults and children from the age of four. Approximately 50 percent of all patients experience a significant decrease in viral load in the body. Amprenavir is taken orally in the form of tablets. Adults take one tablet of 1200 milligrams twice a day. For children, the dosage depends on their body weight. Oral administration results in rapid absorption in the digestive tract. Within the blood, about 90 percent of the active substance binds to plasma proteins. Almost complete metabolization occurs in the liver.
Risks and side effects
There is a risk of side effects from taking amprenavir. These primarily affect the gastrointestinal tract, which is also the case with other protease inhibitors. Thus, affected individuals often suffer from abdominal pain and diarrhea. Skin reactions such as rashes are also possible. In about one percent of all patients, there is a risk of life-threatening complications. These can include Stevens-Johnson syndrome. In the event of side effects of this type, treatment must be discontinued. Metabolic disorders, which include fat redistribution phenomena, represent another undesirable side effect. However, these side effects occur less frequently during therapy with amprenavir than during treatment with indinavir. When amprenavir is used, interactions with other drugs are also conceivable. These are CNS-active drugs such as antidepressants and benzodiazepines. In addition, there is a risk of significant side effects from taking antiarrhythmics and antihistamines at the same time as amprenavir. Doctors also warn of interactions with St. John’s wort extracts. These cause a lowering of the amprenavir level in the blood.Contraindications to the use of amprenavir include pregnancy, renal impairment and hepatic insufficiency. Furthermore, hypersensitivity to the active substance is possible.
