Some drugs used recreationally during sex can have alarming effects on blood pressure. Poppers, if taken together with any of the Viagra-like drugs, can lower blood pressure sufficiently to cause real problems.
Poppers are a recreational drug in the alkyl nitrites family that when inhaled give the recipient a brief head rush. Additionally they relax smooth muscles including in the throat and anus, making poppers especially popular in the gay and bisexual sector.
Some short and long-term health concerns, including blindness, are associated with poppers, so their legal status varies. In the United States, they can be sold only for commercial purposes. Since their composition is similar to compounds used by industry, you can buy them in sex shops and some other retail outlets as “deodorizers,” “air fresheners,” or “DVD head cleaners.”