Antihistamine
The vast majority of marketed H-antihistamines are receptor antagonists and only a minority of marketed compounds are inverse agonists at the receptor. Clinically, H-antihistamines are used to treat allergic reactions and mast cell-related disorders. Sedation is a common side effect of H-antihistamines that readily cross the blood–brain barrier; some of these drugs, such as diphenhydramine and doxylamine, are therefore used to treat insomnia. H-antihistamines can also reduce inflammation, since the expression of NF-κB, the transcription factor the regulates inflammatory processes, is promoted by both the receptor's constitutive activity and agonist (i.e., histamine) binding at the H receptor.
Dapoxetine
The most common effects when taking dapoxetine are nausea, dizziness, dry mouth, headache, diarrhea, and insomnia. Discontinuation due to adverse effects is dose related. According to McMahon in recent study in Asia, the rate of discontinuation is 0.3%, 1.7%, and 5.3% of 1067 studied subjects with placebo, dapoxetine 30 mg, and dapoxetine 60 mg respectively. Unlike other SSRIs used to treat depression, which have been associated with high incidences of sexual dysfunction, dapoxetine is associated with low rates of sexual dysfunction. Taken as needed, dapoxetine has very mild adverse effects of decreased libido (<1%) and erectile dysfunction (<4%).