Amprenavir

Amprenavir is a medicinal substance and belongs to the group of HIV protease inhibitors. The agent is used to treat HIV infections.

What is amprenavir?

Amprenavir is a drug that is 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 Vertex Pharmaceuticals. Amprenavir has been offered 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.

This way the drug will last longer. The half-life is estimated at around 10 hours. In addition, nucleoside reverse transcriptase inhibitors (NRTIs) can be administered at the same time.

Pharmacological effect

Amprenavir works by inhibiting the reproduction of the virus. This counteracts the viral protease of the HIV protease enzyme. HIV protease is of the greatest importance for the development of further virus particles with an infectious effect.

However, if the protease can be inhibited, the spread of the virus in the human organism can be reduced. By reducing any further multiplication of the virus, the viral load eventually decreases. The basis of the effect is the prevention of the splitting off of viral precursor proteins. In this way, immature virus particles that are not infectious are formed.

In contrast to older active substances of this type, the binding mechanism between the active substance and the enzyme is different. For example, patients who react negatively to older protease inhibitors do not experience cross-resistance to amprenavir.

During the clinical trial, a comparison was made between amprenavir and the proven HIV protease inhibitor indinavir. The effectiveness of amprenavir was lower than that of indinavir.

Medical application & use

Like all other HIV protease inhibitors, amprenavir is used to treat infections with the HI virus such as AIDS. During treatment, the agent is combined with other antivirals.

Amprenavir is suitable for both adults and children from the age of four. A significant decrease in the viral load in the body can be seen in around 50 percent of all patients. Amprenavir is taken orally in the form of tablets. Adults take one 1200 milligram tablet twice a day.

In children, the dosage depends on their body weight. Oral ingestion leads to rapid absorption in the digestive tract. Around 90 percent of the active ingredient binds to plasma proteins within the blood. Almost complete metabolism takes place in the liver.

Risks & 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. The affected people often suffer from abdominal pain and diarrhea.

Skin reactions such as rashes are also possible. About one percent of all patients are at risk of life-threatening complications. It can u. a. Stevens-Johnson syndrome. In case of side effects of this kind, the treatment must be stopped. Another undesirable side effect are metabolic disorders, which also include phenomena in the redistribution of fat. However, these side effects are less common with amprenavir than with indinavir.

When using amprenavir, interactions with other drugs are also possible. These are drugs that affect the CNS, such as antidepressants and benzodiazepines. In addition, there is a risk of significant side effects from the simultaneous use of antiarrhythmics and antihistamines with amprenavir. Doctors also warn against interactions with St. John's wort extracts. These cause the amprenavir level in the blood to drop.

Pregnancy, kidney failure and hepatic insufficiency are contraindications for taking amprenavir. Hypersensitivity to the active ingredient is also possible.