Phenylpropanolamine

Phenylpropanolamine (PPA) is a drug of the phenethylamine family used as a decongestant and also as an appetite suppressant. In veterinary medicine, it is used to control urinary incontinence in dogs.

Chemistry
There are four optical isomers of phenylpropanolamine: d- and l-norephedrine, and d- and l-norpseudoephedrine. D-norpseudoephedrine is also known as cathine, and occurs naturally in the stimulant plant Catha edulis (khat). This isomer is commonly used in European medications described as "phenylpropanolamine", whereas in the United States a racemic mixture of d,l-norephedrine is usual.

Just as ephedrine is chemically reduced into methamphetamine, phenylpropanolamine can be chemically reduced into amphetamine. Molecularly, phenylpropanolamine is to ephedrine, just as amphetamine is to methamphetamine, and as cathinone is to methcathinone.

Phenylpropanolamine was also used for the illicit synthesis of other stimulant drugs such as phenmetrazine and 4-methylaminorex, and since phenylpropanolamine was withdrawn from use in humans in the early 2000s (although it is still sold for some veterinary applications) it is now much less available, and this in turn has meant that phenmetrazine and 4-methylaminorex have largely disappeared from the illicit market.

Phenylpropanolamine can be made from cathinone.

Side effects
A scientific study found an increased risk of hemorrhagic stroke in women who used phenylpropanolamine, although it is not clear which isomer is to blame. A study at the Yale University School of Medicine in 1999 had produced similar results. Reports of cases of hemorrhagic strokes in PPA users had been circulating since the 1970s.

A report from the Dept. of Psychiatry, F. Edward Hebert School of Medicine, Bethesda, Maryland in Pharmacopsychiatry states:


 * We have reviewed 37 cases (published in North America and Europe since 1960) that received diagnoses of acute mania, paranoid schizophrenia, and organic psychosis and that were attributed to PPA product ingestion. Of the 27 North American case reports, more reactions followed the ingestion of combination products than preparations containing PPA alone; more occurred after ingestion of over-the-counter products than those obtained by prescription or on-the-street; and more of the cases followed ingestion of recommended doses than overdoses.


 * Failure to recognize PPA as an etiological agent in the onset of symptoms usually led to a diagnosis of schizophrenia or mania, lengthy hospitalization, and treatment with substantial doses of neuroleptics or lithium.

Legal control
In November 2000, the Food and Drug Administration (FDA) issued a public health advisory against the use of the drug. In this advisory, the FDA requested that all drug companies discontinue marketing products containing phenylpropanolamine. The agency estimates that PPA caused between 200 and 500 strokes a year among 18-to-49-year-old users. In 2005 the FDA removed phenylpropanolamine from over-the-counter sale. An item on the agenda of the 2000 Commission on Narcotic Drugs session called for including norephedrine in Table I of United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances

Because of its potential use in methamphetamine manufacture, it is controlled by the Combat Methamphetamine Epidemic Act of 2005. It is still available for use in dogs.