- A colorless crystalline alkaloid, C<sub>20</sub>H<sub>24</sub>N<sub>2</sub>O<sub>2</sub>, resembling quinine and used in treating malaria and cardiac arrhythmias.
- A base (C<sub>20</sub>H<sub>24</sub>N<sub>2</sub>O<sub>2</sub>) isomeric with quinine, and occurring associated with it in some cinchona barks.
- An alkaloid isomeric with, and resembling, quinine, found in certain species of cinchona, from which it is extracted as a bitter white crystalline substance; conchinine. It is used somewhat as a febrifuge.
- An <xref>isomer</xref> of <xref>quinine</xref> that is used as an <xref>antiarrhythmic</xref> agent
- cardiac drug (trade names Quinidex and Quinora) used to treat certain heart arrhythmias