Propanaol has come up in lectures in my Cell Neuroscience course this sem. Of personal interest to me, as its use has become prevalent in the autism population. My last set of docs at Stanford said they preferred its use as it has less side effects compared to other drugs. I have mixed feelings about it effectiveness in my case but I've heard its helping a number of other autistics.
The use of Propranolol (brand names - Inderal, Hemangeol, & InnoPran XL) in autism is actually off-label as some research has suggested that propranolol may be helpful with anxiety, social withdrawal and repetitive behaviors. More research is needed to fully understand its effectiveness in autism.
Some common side effects of propranolol include fatigue, dizziness, cold hands and feet, slow heartbeat, and trouble sleeping. More serious side effects include wheezing, depression, and liver problems.
One concerning side effect is memory impairment. So I have to wonder about its long term impact as we age, as many autistics are on it for many years and years. Are we looking at short term gains and compromising our long term health compounding health issues that already accompany old age.
Some studies have shown that propranolol can impair memory consolidation, which is the process of converting short-term memories into long-term memories. This impairment can be temporary or permanent, depending on the dose of propranolol and the length of time it is taken.One concerning side effect is memory impairment. So I have to wonder about its long term impact as we age, as many autistics are on it for many years and years. Are we looking at short term gains and compromising our long term health compounding health issues that already accompany old age.
In one study, healthy adults who took propranolol for 10 days showed impaired memory for newly learned information. However, their memory for information that they had learned before they started taking propranolol was not affected.
In another study, people with post-traumatic stress disorder (PTSD) who took propranolol for 12 weeks showed improved memory for neutral information, but impaired memory for emotional information.
- Effects of propranolol on memory may vary from person to person (Kindt et al., 2009)
- Memory impact more pronounced if already experiencing memory problems (Raskin et al, 2005)
- Memory impact more pronounced for high doses of propranolol. (Brunet e tal, 2008)
- Memory impact more pronounced if taking propranolol for a long period of time (Raskin et al, 2005)
How does Propananol work?
Molecular Mechanisms: Propranolol is a non-selective beta-blocker that works by inhibiting the beta-adrenergic receptors, which are the receptors for the catecholamine hormones epinephrine and norepinephrine. By blocking these receptors, propranolol reduces the effects of these hormones on the heart and blood vessels, leading to a decrease in heart rate, BP, and cardiac output. Propranolol also has some activity at alpha-adrenergic receptors, which may contribute to its effects on BP. In autism, propranolol's ability to reduce the effects of norepinephrine may be particularly relevant, as increased norepinephrine activity has been linked to hyperarousal and sensory processing issues.
Pathways: In the brain, propranolol has been shown to modulate the activity of several neurotransmitter systems, including the noradrenergic, dopaminergic, and serotonergic systems. Propranolol reduces the release of norepinephrine, which is involved in the body's stress response and has been linked to anxiety and hyperarousal in autistics. Propranolol may also reduce the activity of the dopamine system, which has been implicated in the reward processing and motivation difficulties often seen in autistics. Additionally, propranolol has been shown to enhance the activity of the serotonergic system, which is involved in mood regulation and may play a role in the emotional dysregulation often seen in autistics.
Brain interactions: Propranolol has been found to modulate activity in several brain regions and networks involved in emotional processing, including the amygdala and prefrontal cortex. Propananol has shown to reduce amygdala (fear & anxiety processing) activity in response to emotional stimuli, relevant as many autistics experience heightened fear and anxiety responses to social and sensory stimuli. Propranolol has been found to enhance activity in the PFC (cognitive control & emotion regulation); another area of need for many autistics. Propranolol may also affect brain networks involved in social processing, such as the DMN, which has been implicated in autism. By modulating activity in these brain regions and networks, propranolol may have potential as a treatment for the emotional and social difficulties seen in many autistics.
Molecular Mechanisms: Propranolol is a non-selective beta-blocker that works by inhibiting the beta-adrenergic receptors, which are the receptors for the catecholamine hormones epinephrine and norepinephrine. By blocking these receptors, propranolol reduces the effects of these hormones on the heart and blood vessels, leading to a decrease in heart rate, BP, and cardiac output. Propranolol also has some activity at alpha-adrenergic receptors, which may contribute to its effects on BP. In autism, propranolol's ability to reduce the effects of norepinephrine may be particularly relevant, as increased norepinephrine activity has been linked to hyperarousal and sensory processing issues.
Pathways: In the brain, propranolol has been shown to modulate the activity of several neurotransmitter systems, including the noradrenergic, dopaminergic, and serotonergic systems. Propranolol reduces the release of norepinephrine, which is involved in the body's stress response and has been linked to anxiety and hyperarousal in autistics. Propranolol may also reduce the activity of the dopamine system, which has been implicated in the reward processing and motivation difficulties often seen in autistics. Additionally, propranolol has been shown to enhance the activity of the serotonergic system, which is involved in mood regulation and may play a role in the emotional dysregulation often seen in autistics.
Brain interactions: Propranolol has been found to modulate activity in several brain regions and networks involved in emotional processing, including the amygdala and prefrontal cortex. Propananol has shown to reduce amygdala (fear & anxiety processing) activity in response to emotional stimuli, relevant as many autistics experience heightened fear and anxiety responses to social and sensory stimuli. Propranolol has been found to enhance activity in the PFC (cognitive control & emotion regulation); another area of need for many autistics. Propranolol may also affect brain networks involved in social processing, such as the DMN, which has been implicated in autism. By modulating activity in these brain regions and networks, propranolol may have potential as a treatment for the emotional and social difficulties seen in many autistics.
References
Propranolol side effects: Mayo Clinic. (2021). Propranolol (Oral Route) Side Effects. https://www.mayoclinic.org/drugs-supplements/propranolol-oral-route/side-effects/drg-20071103
Propranolol uses: MedlinePlus. (2022). Propranolol. https://medlineplus.gov/druginfo/meds/a682607.html
Propranolol for autism: Wigham, S., Rodgers, J., South, M., McConachie, H., Freeston, M., & Parr, J. R. (2018). A systematic review of the effectiveness of propranolol for treating emotional and behavioral problems in children and adolescents with autism spectrum disorder. Journal of Autism and Developmental Disorders, 48(3), 760-774.
Mechanisms of action: Ott, J., & Niedermaier, O. N. (2011). Propranolol: a beta-adrenergic antagonist for the treatment of anxiety disorders. Expert Opinion on Pharmacotherapy, 12(4), 573-581.
Brain areas/networks: Aupperle, R. L., Sullivan, S., Melrose, A. J., Paulus, M. P., & Stein, M. B. (2012). A reverse translational approach to quantify approach-avoidance conflict in humans. Behavioural Brain Research, 226(2), 333-338.
Brunet, A., Lissek, S., Nader, K., & Pitman, R. K. (2008). Propranolol for the treatment of acute stress disorder: a randomized controlled trial. The American Journal of Psychiatry, 165(1), 102-108.
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