Ask Dr. Shulgin Online

ARCHIVE:  March 7, 2001

What is Parahexl?

Dear Dr. Shulgin:

I recently looked at the "Scheduled Drugs" list and noticed that most of them were familiar.  The only one I am unfamiliar with is called “Parahexyl.”  I find no reference to it other than in this list. What can you tell me about it? --Renwick

Dear Renwick:

In the early days of cannabis research, tetrahydrocannabinol (THC) was known to be the principal active component of marijuana, but its exact structure was unknown and it had never been synthesized.  

In the early 1940s, there was extensive synthesis and pharmacological study conducted with what was called, correctly, delta-3 THC. It was easy to make, it was active in both animals and man, and it was amenable to structural manipulation. It was found that the replacement of the 5-carbon amyl group with other groups could lead to increased potency and possible medical use. An early example was the substitution of the 6-carbon hexyl group, which resulted in the orally active homologue called Parahexyl (or Synhexyl or Pyrahexyl).

A quarter of a century later, when the structure and synthesis of the correct THC (delta-1 THC) was known, the variations of the amyl group were explored again, but with a direct comparison to natural THC. The entire delta-3 world faded completely from view.  

In 1971, there was an International Drug Control Treaty, from a U.N. Convention on Psychotropic Substances. The United States signed this treaty in 1980. 

In 1982, the parties to the 1971 treaty proposed the illegalization of Parahexyl, and the U.S. Secretary of Health recommended that it be placed in Schedule I of the U.S. Controlled Substances Act. It became a Schedule I drug on December 22, 1982, thus bringing it out of deserved obscurity and into public view once again.

-- Dr. Shulgin

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