Mr. Hobbs,
The original component of Elsinore Pill is ephedrine, caffeine and phenobarbital. What is the purpose of adding phenobarbital, to reduce the side effects of ephedrine or caffeine?

yesure,

The Elsinore Pill was for asthma, so the phenobarbital had something to do with treating asthma.

Mr. Hobbs,

Phenobarbital has no direct pharmacologic effect to treat asthma. It is used as an anticonvulsant clinically. Since barbiturates have affinity for the GABA receptor in the CNS, I reasonably assume that phenobarbital of Elsinore pill might reduce the side effects of ephedrine or caffeine.

yesure,

As you noted originally, I assume the phenobarbital is added to ephedrine and caffeine, or ephedrine and theophylline to counter the stimulating effects.

It has a sedating effect.

If you do a Google search for the “Elsinore Pill” it shows that it contained ephedrine, caffeine and phenobarbital, and was given to asthma patients.

A doctor noticed that these patients were losing weight.

He later gave a modified version of the Elsinore Pill that did not contain the phenobarbital.