Ephedra is a Chinese shrub which has been used in China for medicinal purposes for several thousand years. The pure alkaloid ephedrine was first isolated and characterised by Nagai in 1885. It was then forgotten until it was rediscovered by Chen and Schmidt in the early 1920s. Its actions on the adrenoceptors could be classified into separate alpha and beta effects--a defining moment in the history of autonomic pharmacology. Ephedrine became a highly popular and effective treatment for asthma, particularly because, unlike adrenaline (until then the standard therapy), it can be given by mouth. Ephedrine as a treatment for asthma reached its zenith in the late 1950s, since when there has been a gradual and inevitable decline in its therapeutic use. From mainstream medicine, ephedrine moved into the twilight zone of street drugs and nutritional supplements. Ephedra and ephedrine products are now banned in many countries, as they are a major source for the production of the addictive compound methamphetamine (crystal meth).

1. The effects of 1 h intravenous infusions of equimolar amounts of two putative 5‐hydroxytryptamine (5‐HT) renal prodrugs, 5‐hydroxy‐L‐ tryptophan (5‐HTP, 10 micrograms kg‐1 min‐1) and gamma‐L‐glutamyl‐5‐ hydroxy‐L‐tryptophan (glu‐5‐HTP, 16.6 micrograms kg‐1 min‐1) were examined in five healthy male volunteers in a randomised, placebo‐ controlled, cross‐over study. 2. Both compounds increased urinary excretion of 5‐HT and there was greater extra‐renal formation of 5‐HT following 5‐HTP administration than after glu‐5‐HTP. 3. Glu‐5‐HTP was significantly antinatriuretic. 5‐HTP reduced mean urinary sodium excretion but this effect was not statistically significant. 4. 5‐HTP, but not glu‐5‐HTP, significantly increased plasma aldosterone. There was no increase in plasma renin activity with either compound. 5. There were no significant changes in pulse rate or blood pressure. Two subjects complained of nausea at the end of 5‐HTP infusion but none had any adverse reactions with glu‐5‐HTP. 6. The results of this study suggest that both prodrugs generate 5‐HT in man and that glu‐5‐HTP is antinatriuretic. The glutamyl derivative may have greater renal specificity than 5‐HTP and, as a result, causes less systemic side effects.

The Royal Infirmary, Edinburgh EH3 9YW 1 y-L-glutamyl-L-dopa (gludopa) and placebo were given by intravenous infusion to 12 healthy salt replete men for 10 h in a single-blind randomised fashion. 2 Gludopa caused a cumulative natriuresis of 46.5 mmol compared with placebo with a biphasic pattern and this was associated with a small reduction in body weight. 3 A small fall in arterial blood pressure and rise in pulse rate was seen with gludopa. 4 Plasma renin activity, atrial natriuretic peptide and urine kallikrein excretion were unchanged by gludopa but a small fall in urine aldosterone excretion, urine flow rate and free water clearance occurred. 5 The renal effects of gludopa are modest and last for only a few hours after the start of infusion.

The liquorice plant (Glycyrrhiza glabra, the Sweet Root): its form and distribution

1 Human alpha atrial natriuretic peptide (ANP) was infused intravenously for 1 h in eight healthy salt-replete men on two occasions, with and without pretreatment with (+)-sulpiride. 2 ANP increased sodium excretion and urine flow rate but did not alter blood pressure or plasma renin activity. 3 (+)-sulpiride had no significant effect on baseline creatinine clearance, sodium excretion or urine flow rate and did not alter the increases in these parameters with ANP. 4 It is unlikely that the renal effects of ANP are mediated by dopamine DA1-receptors in man.