Nucleoside analogue
reverse transcriptase inhibitors (NRTIs)
Nucleoside analogue reverse transcriptase inhibitors (NRTIs) were the first antiretroviral drugs to be developed. Nucleoside analogs are synthetically created to mimic naturally occuring nucleotides. Nucleosides resemble nucleotides but they lack a phosphorus group. Nucleosides are administered because they are more easily transported across the cell membranes than charged nucleotides. To be active, the body must phosphorylate the nucleoside within the cell. Once phosphorylated, the nucleotide can be incorporated into a DNA or RNA chain.
NRTIs work by competing with naturally occurring nucleotides. Reverse transcriptase assembles nucleotides to create a DNA chain that contains the viral genes. As reverse transcriptase attaches an NRTI nucleotide to build a DNA chain, it causes a DNA chain termination. The termination is due to the intentional absence of a bond needed to properly attach a nucleotide.
Drugs in this class include:
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