BB and delirium

Q: How Beta-blockers directly contribute to delirium?



Answer: By decreasing Melatonin

Although delirium is usually multi-factorial and very hard to pin-point on one exclusive culprit. Various cardiac drugs including beta-blockers, digoxin, diuretics, and anti-arrhythmia agents can be a direct or indirect contributor.  The objective of this question is to bring to discussion the interesting mechanism by which B-blockers induce delirium. Beta-blockers reduce the level of melatonin and may cause a direct contribution to delirium. This reduction in melatonin is due to a specific decrease in production of melatonin via inhibition of brain adrenergic beta1-receptors as evidenced by decreased urinary secretion of melatonin. Other mechanisms have also been proposed like BBs effect on serotonin (5-HT) receptors. 

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 References:

1. Brismar K, Mogensen L, Wetterberg L: Depressed melatonin secretion in patients with nightmares due to beta-adrenoceptor blocking drugs. Acta Med Scand 1987; 221:155–158 

2. Fisher AA, Davis M, Jeffery I: Acute delirium induced by metoprolol. Cardiovasc Drugs Ther 2002; 16:161–165

3. Dimsale JE, Newton RP, Joist T. Neuropsychological side effects of beta-blockers. Arch Intern Med1989;149:514–25.