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.
Finasteride
The 2010 Cochrane review found that compared with placebo, men taking finasteride are at increased risk for impotence, erectile dysfunction, decreased libido, and ejaculation disorder for the first year of treatment; the rates of these effects became indistinguishable from placebo after 2–4 years and these side effects usually got better over time. Another 2010 review found that when used for hair loss finasteride increased rates of sexual problems. A 2016 meta-analysis found that sexual dysfunction, including erectile dysfunction, loss of libido, and reduced ejaculate, may occur in 3.4 to 15.8% of men treated with finasteride or dutasteride. This adverse effect has been linked to lower quality of life and can cause stress in relationships.