Nelfinavir,
ritonavir, and saquinavir are predicted to increase the levels of calcium- channel blockers that are substrates of CYP3A4. The manufacturers of
amprenavir similarly predict that it will increase the levels of
diltiazem, nicardipine,
nifedipine and
nisoldipine. Atazanavir has been seen to raise
diltiazem levels (2- to 3-fold) and is therefore predicted to raise
verapamil levels.
Undertake concurrent use with caution. Monitor for
toxicity, such as hypotension, dizziness, flushing and palpitations.