HTR2A and insomnia: For example, about 10 categories of drugs are associated with insomnia, including antihistamine (e.g., doxylamine32), anxiolytics (e.g., etizolam33), and antipsychotics (e.g. melperone34), which affect GABA-A, D2 dopaminergic and 5HT2A serotonergic and other receptors to treat insomnia.