There are five classes of HIV drugs used to treat AIDS, including nucleoside/nucleotide reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, protease inhibitors, fusion/entry inhibitors, and integrase inhibitors. Treatment should begin when the CD4 count drops below 500 or when severe HIV symptoms appear. While drugs have reduced viral loads and opportunistic infections, they require strict adherence to multiple daily pills and can cause side effects like nausea and bone problems. Doctors monitor treatment response by measuring viral load and CD4 counts every 3-4 months.