Protease inhibitors (PI) are a class of medication developed to fight HIV infection. They work by blocking the protease enzyme, which results in copies of HIV that are unable to infect other cells. There are only a few FDA-approved PIs, all of which share a common profile of side effects that patients experience to varying degrees; there are also side effects particular to certain PIs.
Common Side Effects
PIs can affect metabolic processes in patients, with varying results. One is high blood sugar and subsequent development of diabetes, and another relates to how the body absorbs nutrients, including fats. This is called lipodystrophy and results in altered fat distribution, for example around the belly and breasts; loss of fat in the face; and loss of muscle in the limbs. There are also increased levels of fat in the bloodstream, with consequences of their own such as cardiovascular disease or pancreatitis. Liver toxicity is another concern, which is magnified in those with existing liver disease like chronic viral hepatitis. This is why blood tests that monitor liver function as well as cholesterol and triglyceride levels are routine in patients on PI therapy.
Indinavir
With indinavir, kidney stones are a possible complication that can present with blood in the urine, especially in pediatric patients. Muscle and back pain are also common side effects, along with itchiness and rash.
Tipranavir
Tipranavir has been associated with rashes, urticaria (hives) and possible sensitivity to light. However, the most common toxicity occurs in the liver, which can be a concern with all PIs but especially this one.
Darunavir
Gastrointestinal complaints such as diarrhea, abdominal pain, nausea and vomiting can occur with darunavir usage. Users can also suffer from headaches, and occasionally a rash that resolves with time.
Fosamprenavir
Common side effects of fosamprenavir include diarrhea, nausea and vomiting, headache, rash and abdominal pain. The diarrhea can be severe and is among the top reasons users discontinue taking the drug.
Ritonavir
The most common adverse effects of ritonavir are weakness, nausea and vomiting, abdominal pain, anorexia, diarrhea and feelings of altered sensation. Pancreatitis is a complication that can have fatal consequences due to marked triglyceride elevations with drug usage. Flushing is a common cardiovascular side effect, and muscle pain is a common musculoskeletal side effect.
Saquinavir
Resistance rapidly develops to saquinavir, so monotherapy (use of only one drug) is not ideal. The adverse effects most often seen are typically mild. These include diarrhea, nausea and vomiting and abdominal pain.
Kaletra
Kaletra is a formulation of both lopinavir and ritonavir, and the most commonly reported adverse effect is abdominal pain. Diarrhea is another common side effect, along with flatulence, headache, weight loss, muscle pain, depression, insomnia, decreased libido and altered sensations.
Nelfinavir
The most common adverse reaction with nelfinavir is diarrhea, which is usually mild. Severe side effects include muscle weakness, abdominal pain and occasional hypersensitivity reactions (wheezing, rash).
Atazanavir
With altazanavir, rash is quite common and usually lasts a little more than a week. Other adverse effects seen frequently include diarrhea, abdominal pain, nausea and vomiting, peripheral neuropathy and headache.
References
- Protease Inhibitors
- "Principles and Practice of Pediatric Infectious Diseases, 3rd Edition;" S. Long et al.; 2008
- "Rosen's Emergency Medicine, 7th Edition;" J. Marx, M.D. et al.; 2009
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