Medica Scandinavia clearly demonstrates the melatonin-disrupting effects of beta blockers. Melatonin levels were measured against those of a control group. As a whole, melatonin levels fell significantly in patients compared to controls, and wakefulness increased. Metoprolol decreased melatonin more than atenolol or propranolol. The three patients with the lowest levels of melatonin reported nightmares.
Beta blockers suppress serotonin as well as melatonin.
Thus, it is not surprising that the Physicians Desk Reference lists mental depression, fatigue, short-term memory loss, insomnia and emotional lability as some of the side effects of Inderal and other beta blockers. Apparently unaware of the role beta receptors play in getting a good night's sleep, the manufacturer of Inderal, Wyeth-Ayerst, recommends that these drugs be taken at bedtime. Two benzodiazepine type drugs have been shown to suppress melatonin and disrupt sleep patterns in humans and rodents. Valium and Xanax both cause decreased production of melatonin at night. This is an important discovery because it was previously assumed from studies on blood cells that AD patients had too much SAMe.