One of the commonest side-effects associated with indinavir (Crixivan) is kidney stones or ‘nephrolithiasis’^{[1][2][3][4][5]}. Its symptoms are pain on passing urine, pain along the side of the body and ‘gravel’ in the urine. The pain associated with kidney stones can be severe. About one in 25 people treated with indinavir develop kidney stones. Drinking a large amount of water at the same time taking the indinavir reduces the risk of this side-effect.

People with high concentrations of indinavir in their blood are more likely to experience kidney and urinary side-effects. Kidney stones have been seen more frequently in people taking indinavir with ritonavir, because indinavir levels are boosted. Drug-level monitoring, if available, can determine indinavir levels and indicate if dose reductions are necessary and safe in terms of preserving the anti-viral effect of the treatment. Studies have shown that dose reductions of up to 400mg can reduce kidney problems without increasing the chance of viral rebound^[6][7].

If a patient develops kidney stones while taking indinavir, it may be necessary to interrupt indinavir for one to three days, or to stop taking it altogether.

The most commonly reported side-effect from long-term use of indinavir is increased levels of bilirubin in the blood^[8]. Although not dangerous, this side-effect causes yellowing of the skin and the whites of the eyes, and can be stigmatising. Hyperbilirubinaemia is more common in patients with a polymorphism in the gene for the enzyme that removes bilirubin from the body^[9].

Indinavir may cause a worsening of pre-existing low level of platelets in the blood or it may cause anaemia. One study has found that people taking indinavir have an increased risk of blood clots, although further research into this association is needed^[10].

Short-term side-effects of indinavir use tend to be more resolve after the first few weeks of treatment. These include nausea, headache, fatigue, abdominal pain, vomiting, rash, dry skin and strange tastes in the mouth. Intestinal wind and bloating have also been reported.

Other side-effects include ingrowing toe nails and inflammation around the nail, as well as severe skin dryness and cracked lips^[11][12]. These occur in 1 to 4% of people taking the drug. There is some evidence that reducing the dose of indinavir may reduce the severity of these side-effects. However, this must only be attempted if it is judged to be safe in terms of controlling viral load.

As a class, protease inhibitors have been associated with a syndrome of fat and metabolic irregularities. This includes altered fat distribution, high lipid levels in the blood, insulin resistance, diabetes, increased levels of blood sugar and increased bleeding in haemophiliacs^[13]. For more details see Body fat and metabolic changes whilst on treatment.