antibioticsbooks

222 PART 5 Antiviral Drugs
Spectrum
In addition to being used to treat the HIV virus,
several of these drugs (tenofovir, emtricitabine,
lamivudine) have clinically useful activity against
hepatitis B virus (HBV).
Adverse Effects
Extremities: Peripheral neuropathy is seen as a
delayed, slowly progressive adverse effect in
some patients taking didanosine or stavudine
(and especially in combination).
Gastrointestinal: NRTIs tend to have less GI toxicity
(nausea, vomiting, diarrhea) than many
antiretrovirals, but zidovudine and didanosine
may be problematic.
Hematologic: Bone marrow suppression (anemia,
neutropenia) occurs frequently with zidovudine,
and rarely with other NRTIs.
Hypersensitivity: In a minority of patients, abacavir
use is associated with a hypersensitivity
reaction manifesting with fever, rash, and
flulike symptoms days to weeks after starting
therapy. Continuation of or rechallenge with
abacavir in patients experiencing this syndrome
can be fatal. Patients at highest risk for
this toxicity can be identified by a genetic test
for the HLA B 3 5701 allele before starting
therapy; patients testing positive should not be
offered abacavir.
Metabolic: Lactic acidosis, hepatic steatosis, and
pancreatitis are part of a complex of toxicities
suspected to be of mitochondrial origin that are
a classwide adverse effect of NRTIs. Mortality
can be high if symptoms are not recognized