The HIV Drug Classes Explained

Drugs that treat HIV, known as antiretroviral medications, are grouped in various classes based on the methods the drug uses to attack the virus. HIV treatment regimens include drugs from multiple classes, to improve their combined effectiveness and help prevent the development of drug resistance. Here are brief descriptions of the classes and how they work.

ENTRY AND FUSION INHIBITORS (EIs)
Drugs in this class help block HIV from binding, fusing, and entering T cells. They are always taken with other HIV medication.

INTEGRASE STRAND TRANSFER INHIBITORS (INSTIs)
Drugs in this class block integrase, an enzyme HIV needs in order to reproduce. HIV uses integrase to insert its viral DNA into the DNA of T cells. Blocking the integration process prevents HIV from replicating. They are always taken with other HIV medication.

NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS
(NRTIs, also known as nukes)
Drugs in this class block reverse transcriptase, an enzyme that HIV needs in order to reproduce. HIV uses reverse transcriptase to convert its RNA into DNA, blocking the reverse transcription process prevents HIV from replicating. They are always taken with other HIV medication.

NONNUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS
(NNRTIs, also known as nonnukes)
Drugs in this class also block reverse transcriptase, as NRTIs do, but in a different way. They are always taken with other HIV medication.

PHARMACOKINETIC ENHANCER/ CYP3A INHIBITORS
(PKEs, also known as boosters)
Drugs in this class boost the effectiveness of antiretroviral medication. When the two are taken together, the pharmacokinetic enhancer slows the breakdown of the other drug, which allows the drug to remain in the body longer at a higher concentration. They are always taken with other HIV medication.

POST-ATTACHMENT INHIBITORS (PAIs)
Drugs in this class bind to CD4 cells after HIV has attached to them, but still inhibit the HIV virus from successfully infecting those cells. They are always taken with other HIV medications.

PROTEASE INHIBITORS (PIs)
Drugs in this class block activation of protease, an enzyme HIV needs to develop. Blocking protease prevents immature forms of HIV from becoming a mature virus capable of infecting other T cells. They are always taken with other HIV medication.

SINGLE-TABLET REGIMENS (STRs)
These are fixed-dose pills that combine multiple anti-HIV medications (often from more than one class of drug) into a single tablet, which is usually taken just once a day. They do not need to be taken with other HIV medication.