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Pipradrol (Meratran) is a mild central nervous system stimulant (norepinephrine-dopamine reuptake inhibitor) that is no longer widely used in most countries due to concerns about its abuse potential, although this is less of a problem than with other stimulants that still are in current use such as methylphenidate. Pipradrol is still used in some European countries, and even rarely in the USA. Pipradrol was developed in the 1940s, and found use initially for treating obesity. It was subsequently used for the treatment of a variety of other conditions such as narcolepsy, ADHD, and most particularly for counteracting the symptoms of senile dementia, this being the only application for which it is still used medically. Pipradrol proved useful for these applications as its relatively mild stimulant effects gave it a good safety profile compared to stronger stimulants. It was also trialled as an adjutant treatment for depression and schizophrenia although it was never widely used for these purposes.
Pipradrol was made illegal in many countries in the late 1970s, at the same time as many other drugs which had a history of abuse. The relatively mild stimulant effects of pipradrol meant that it was scheduled under the less restrictive classes in most countries (i.e. Class C in United Kingdom and New Zealand) but was still considered of sufficient abuse potential to be made an illegal drug. It is now an obscure compound that is virtually unknown as an illicit drug of abuse, but is still used for some scientific research, often as a comparison drug for testing other stimulants against.
Dosage is between 0.5 and 4 milligrams per day, typically taken as a single dose in the morning as the long duration of effects of pipradrol (up to 12 hours) means insomnia can be a problem especially if it is used at higher doses or taken too late in the day.
Cyclization of the side chain onto the nitrogen atom leads to compounds with sedative and tranquilizing activity. The lack of structural specificity, that is, the fact that both positional isomers show the same activity, is notable.
Thus, condensation of the Grignard reagent from 2-bromopyridine with benzophenone affords the tertiary carbinol. Catalytic reduction in acetic acid leads to selective hydrogenation of the heterocyclic ring and formation of Pipradrol. Analogous sequence using an organometallic derived from 4-bromopyridine gives Calmeran.
- Tilford, Charles H; Werner, Harold W U.S. Patent 2,624,739 (1953).
- Gelvin EP, McGavack TH, Kenigsberg S. (1955). "Alpha-(2-piperidyl) benzhydrol hydrochloride (pipradrol) as an adjunct in the dietary management of obesity". N Y State J Med 55 (16): 2336–8. PMID 13244858.
- Schumann, E. L.; VanCampen, M. G. and Pogge, R. C. U.S. Patent 2,804,422 (1957).
- Tilford, Charles H.; Shelton, Robert S.; Campen, M. G. van (1948). "Histamine Antagonists. Basically Substituted Pyridine Derivatives". Journal of the American Chemical Society 70 (12): 4001–4009. doi:10.1021/ja01192a010. PMID 18105922.