Duplicitous drugs: the history and recent status of look-alike drugs

(-)Ephedrine and caffeine mutually potentiate one another's amphetamine-like stimulus effects

Using rats trained to discriminate 1 mg/kg of (+)amphetamine (ED50 = 0.4 mg/kg) from saline vehicle in a two-lever drug discrimination procedure, it was shown that (-)ephedrine (ED50 = 4.5 mg/kg), but not (+)ephedrine, substitutes for the (+)AMPH stimulus. It was also shown that caffeine (ED50 = 12.9 mg/kg) can substitute for (+)amphetamine in a dose-related fashion. Doses of (-)ephedrine and caffeine, which produced < or = 1% drug-appropriate responding when administered alone, were able to enhance each other's stimulus effects when administered in combination such that there was a twofold leftward shift in their respective dose-response curves. Furthermore, stimulus generalization occurred when a dose of caffeine that produced saline-appropriate responding when administered alone was administered in combination with (+)ephedrine. It would appear that low doses of (-)ephedrine and caffeine may mutually potentiate one another's stimulus effects in (+)AMPH-trained rats, and that a combination of caffeine and (+)ephedrine result in altered stimulus character when compared to comparable doses of either agent administered alone.

Prevalence and demographic factors of stimulant use

The use of stimulants for recreation purposes has increased considerably during the 20th century. Cocaine was first considered to be a drug of potential abuse during the First World War but was only perceived as a serious threat when it became widely used in socially and economically deprived urban areas of the USA in the 1980s. Use of amphetamines was common among certain occupational groups as a means of remaining alert until the 1950s, when they were seen to be abused by a small minority of recreational users. Controls were then introduced in most developed countries. The public health issue of stimulant use is that of finding a balance between the prevention of serious social or personal harm caused by abuse of these drugs while not impeding their beneficial use.

Phenylpropanolamine-induced psychosis. Potential predisposing factors

Phenylpropanolamine (PPA) is a sympathomimetic drug contained in numerous over-the-counter and prescription decongestants and appetite suppressants. A range of adverse effects have been reported, including neuropsychiatric reactions in patients known to be taking recommended doses. Given that psychiatric symptoms are not included in the manufacturer's lists of adverse drug reactions, the incidence may be significantly higher. We report a cae of paranoid psychosis following use of a decongestant containing PPA and summarize the case report literature of psychiatric adverse effects to PPA in which doses were known and stated to be within recommended guidelines. A pattern of possible risk factors emerges from these reports. These may include 1) symptoms or history of mood spectrum disorder, 2) history of psychosis, 3) female sex, 4) family history of psychiatric disorder. The possibility that a higher incidence of adverse events occurs in a vulnerable population has not been systematically addressed, and seems called for. We recommend that physicians specifically inquire about patients' use of decongestants and diet aids. In half of the above cases, symptoms resolved without the use of antipsychotics.

The discriminative stimulus properties of legal, over-the-counter stimulants administered singly and in binary and ternary combinations

Ninety-six male Sprague-Dawley rats were trained in one of seven drug versus saline (SAL) discrimination (DD) tasks under a variable-ratio 5-15 schedule of food-motivated lever press responding. Three groups of rats (n = 12/group) were trained to discriminate between one of the legal over-the-counter (OTC) stimulants--caffeine (CAF), ephedrine (EPHED), phenylpropanolamine (PPA), and SAL. Three other groups (n = 12/group) were trained to discriminate between one of three binary stimulant combinations--CAF+EPHED, CAF+PPA, EPHED+PPA, and SAL. The seventh group of rats (n = 24) was trained to discriminate between SAL and a ternary combination of the OTC stimulants, CAF+EPHED+PPA. Generalization tests were conducted with each of the OTC stimulants and the controlled stimulants--amphetamine (AMPHET) and cocaine (COC). The data suggest: 1) there is cross-generalization between some OTC combinations and controlled stimulants; 2) full generalization between the OTC and controlled stimulants were demonstrated in rats trained to discriminate two of the binary stimulant combinations from SAL; 3) drug mixtures are not perceived as new entities distinct from their component elements; 4) training dose-ratio may influence the characteristics of mixture discriminations; 5) stimulus overshadowing may be a factor determining drug mixture cues, and 6) the DD properties of aggregate drug compounds may function within a euclidean metric space. We propose that some binary OTC stimulant combinations may effectively function as a methadone-like replacement therapy in cocaine dependence.

Non-prescription sympathomimetic agents and hypertension

In recent years, considerable attention has been focused on the pressor effects of nonprescription sympathomimetic agents. The impact and usage of these agents especially ephedrine, pseudoephedrine, phenylpropanolamine and phenylephrine, in hypertensive patients has been the topic of constant debates. The present review is an attempt to report and evaluate all the clinical trials and cases of pressor reactions associated with these 4 agents. The study protocols used in these clinical trials are examined and comments made on any diversion from the standard design. Many factors are found to cause the discrepancies in the data available. It is concluded that ephedrine and phenylpropanolamine are best avoided by hypertensive patients due to higher probability of causing pressor reactions. Data on pseudoephedrine and phenylephrine appear to indicate non-significant effects on blood pressure of normotensive subjects when used at the recommended oral dose as nasal decongestants. Phenylephrine is also commonly employed in nasal and eye drops and the limited data available appear to support its usage in hypertensive patients. However, it is noted that most of the clinical trials involve normotensive subjects and the majority of the results could not be verified due to inadequacies in the study design. This paucity and inconclusive information on hypertensive patients warrants further investigations with emphasis on the study protocols used.