A PI (protease inhibitor) for HIV is an antiretroviral that blocks the HIV protease enzyme, preventing cleavage of viral polyproteins and producing noninfectious immature virions. PIs are used in combination antiretroviral therapy to reduce viral load and preserve immune function. They can cause side effects such as gastrointestinal upset, metabolic changes (lipid and glucose abnormalities), and significant drug interactions via CYP3A4, so monitoring and dose adjustments are often needed.

An HIV drug resistance test detects whether a person’s HIV carries mutations that make antiretroviral medicines less effective. Genotypic tests identify specific resistance mutations in the virus’s genes; phenotypic tests measure how well the virus grows in different drug concentrations. It’s done from a blood sample at diagnosis, before or during therapy, or if viral load rises, and guides choice of effective treatment.

HIV‑1 genotype "not detected" means the resistance test did not find HIV mutations linked to antiretroviral drug resistance. This may indicate no resistant virus or that the viral load was too low for detection. It doesn’t rule out archived or minority resistant variants. Correlate the result with your current viral load and treatment history and discuss repeat testing or management with your clinician.

Two types of HIV resistance are transmitted (primary) resistance and acquired (secondary) resistance. Transmitted resistance occurs when a person is infected with an HIV strain already carrying drug-resistance mutations. Acquired resistance develops during treatment when the virus mutates due to incomplete viral suppression—often from poor adherence, suboptimal drug levels, or drug interactions—reducing antiretroviral effectiveness.

PI (protease inhibitor) drugs are antiretroviral medicines that block the viral protease enzyme, preventing HIV from maturing and replicating. They’re used in HIV therapy, often with boosters like ritonavir or cobicistat. Common side effects include gastrointestinal upset, metabolic changes (hyperglycemia, dyslipidemia, lipodystrophy) and significant drug–drug interactions via CYP450, so monitoring and dose adjustments are often needed.

Common HIV drug classes include: Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) — block reverse transcriptase to stop viral replication; Non‑nucleoside reverse transcriptase inhibitors (NNRTIs) — bind reverse transcriptase differently; Protease inhibitors (PIs) — prevent viral protein processing; Integrase strand transfer inhibitors (INSTIs) — block integrase to stop viral DNA integrating into host cells. They’re used together in combination antiretroviral therapy.