Abstract
Quercertin is a compound so widely distributed in plants that it is difficult to avoid. Significant quantities of quercetin are found in such ubiquitous foodstuffs as onion, grapes, tomato, apples and tea. Quercertin is an antioxidant and free radical scavenger and is so much revered by the general public as a treatment for just about anything. In fact, robust data on therapeutic benefit are hard to come by, although animal experiments have strongly indicated that quercetin is a potent cognitive enhancer. In this issue, Joshua Broman-Fulks and colleagues report on the largest human study of quercetin and its effects on cognition (only the second human study to be published). In a double-blind design, 941 participants were randomised to placebo, 500mg quercetin daily or 1000mg quercetin daily for 12 weeks. At the end of this period, quercetin supplementation was reflected in plasma quercetin concentrations in a dose-dependent fashion. However, those changes in quercetin exposure had no effect on cognitive function in any domain. (Or to be more precise, quercetin supplementation showed no greater beneficial effects than placebo.) All three groups improved their test scores, showing, perhaps, the effects of training and expectation. Nothing in this appropriately powered, well conducted study suggests any role for quercetin as a cognitive enhancer.
Cortisol plays a major part in the development of depression, to the extent that it is probable that all depression results from some degree altered cortisol responsiveness. The best and most cited example of the potency of cortisol in this respect is that where cortisol levels are pathologically high in Cushing Syndrome, depression affects almost everyone. When cortisol levels are normalised, the depression abates (Kelly et al., 1996). Extrapolating from these observations, psychiatrists wondered whether reducing cortisol levels in non-Cushing’s subjects might treat depression. Paul David Singalas and co-workers review the role of metyrapone in this issue. Metyrapone inhibits cortisol synthesis and so reduces cortisol plasma levels. Most of the studies of metyrapone have been limited in size, scope and scientific rigour but all have been broadly positive. The best conducted study showed an effect size of 0.6 when metyrapone was added to standard antidepressants. Clearly more studies are required but metyrapone shows considerable promise – only its lack of patent protection militates against its more widespread testing and use.
In the second review article in this issue, Praharaj and Sharma report on the use of amantadine for olanzapine-induced weight gain. Amantadine is a dopamine releaser and re-uptake inhibitor that started out as an antiviral agent used for influenza. It also reduces appetite and is associated with weight loss. As such it seemed an excellent candidate to prevent or reverse the often profound weight gain seen with olanzapine. Praharaj and Sharma uncovered six studies examining the use of amantadine with olanzapine but only two met their inclusion criteria. These two studies combined showed a statistically significant and clinically worthwhile advantage over placebo in terms of weight reduction and frequency of weight loss. Amantadine thus is a suitable treatment for olanzapine-associated weight gain but is perhaps a second-line treatment after the better established metformin which has additional antidiabetic properties.
Two further letters-to-the-editor demonstrate the need to expect the unexpected even when prescribing commonly used drugs. Hayward and Luft describe a peculiar presentation of delirium caused by a combination of lithium clomipramine and Channing and colleagues demonstrate the dangers of using successive doses of long- acting drugs (clonazepam in this case) in acute situations – the danger of accumulation should not be underestimated.