The replacement of a hydrogen atom with a fluorine atom in certain compounds to facilitate passage through the blood–brain barrier, as is desirable in central nervous system pharmaceutical agents, is a common practice due to the corresponding increase in lipophilicity granted by this substitution.

[4][medical citation needed] Analgesic dose (50% inhibition of response to tail-clamp) = 20 mg/kg (mouse; i.p.).

[4][medical citation needed] Effect on blood pressure: 0.5 mg/kg (rat; i.v.)

[4][medical citation needed] The Federal Analogue Act, 21 U.S.C.

§ 813, is a section of the United States Controlled Substances Act, allowing any chemical "substantially similar" to an illegal drug (in Schedule I or II) to be treated as if it were also in Schedule I or II, but only if it is intended (ref 1) for human consumption.