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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 3 of 3. This is the beginning of the thread.
Posted by super on June 14, 2001, at 12:47:22
I'm puzzled, and this is an entirely intellectual matter for me since I can't even tolerate SSRIs, BUT why do they cause weight gain? I was just reading an article that stated that compulsive overeating is a result of seratonin deficiency. If SSRIs increase seratonin in the brain, wouldn't they help you eat less and therefore loose weight?
Posted by Elizabeth on June 14, 2001, at 15:12:52
In reply to WHY do SSRIs cause weight gain???, posted by super on June 14, 2001, at 12:47:22
> I'm puzzled, and this is an entirely intellectual matter for me since I can't even tolerate SSRIs, BUT why do they cause weight gain? I was just reading an article that stated that compulsive overeating is a result of seratonin deficiency. If SSRIs increase seratonin in the brain, wouldn't they help you eat less and therefore loose weight?
The "serotonin deficiency" hypothesis is just that: a guess. (Although an awful lot of Redux was sold based on that guess.) Serotonin is considered a neuromodulator, a neurotransmitter which has long-term effects on many functions of the brain. Last I checked, 14 different serotonin receptor subtypes had been identified. Like other receptor subtypes (e.g., alpha- and beta-adrenergic receptors), the various types of serotonin receptors have different effects, some of which may oppose each other. Because different people have different numbers and levels of sensitivity of each type of serotonin receptor, it should be expected that serotonin reuptake blockade will have different clinical effects on one person than on another.
The specifics of SSRI-associated weight gain are not known for certain, but one hypothesis is that down-regulation of the 5-HT2c receptor subtype is involved.
-elizabeth
Posted by Sunnely on June 16, 2001, at 1:14:03
In reply to WHY do SSRIs cause weight gain???, posted by super on June 14, 2001, at 12:47:22
Hi Super,
SSRIs have similarity to the appetite-suppressant drug dexfenfluramine (Redux), now off the market, with regard to their serotonergic effect. Therefore, it would be expected that all SSRIs should exert similar appetite-suppressant action and subsequent weight loss. However, case reports indicate evidence to the contrary. In addition, although the appetite-suppressant action of fluoxetine (Prozac) is well recognized, long-term follow-up studies in depressed patients and in obese nondepressed patients reveal that its weight-reducing effects are transient, even leading to a gain in body weight. Similarly, paroxetine (Paxil) and citalopram (Celexa) have also been associated with weight gain. These latter observations are unexpected because Paxil and Celexa are highly potent and selective SSRIs, respectively.
Although SSRIs are termed "selective serotonin reuptake inhibitor" drugs, they actually do not act purely and only on serotonin alone. It appears that the paradoxical weight gain observed with SSRIs rest on the interaction of serotonin with multiple mechanisms. Aside from the serotonin receptors being involved, it appears that other receptors play a role in SSRI-induced weight gain. These include histamine receptor (H1), dopamine (DA) receptors, and norepinephrine (NE) receptors. In addition, the role of glutamate, nitric oxide (NO), and leptins in SSRI action requires further clarification.
Finally, the neurobiology of depressive illness itself, and recovery from it, plays a major contributing factor to individual response to these drugs.
Bottom line is, the exact mechanism as to the SSRI-induced weight gain remains unclear.
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> I'm puzzled, and this is an entirely intellectual matter for me since I can't even tolerate SSRIs, BUT why do they cause weight gain? I was just reading an article that stated that compulsive overeating is a result of seratonin deficiency. If SSRIs increase seratonin in the brain, wouldn't they help you eat less and therefore loose weight?
This is the end of the thread.
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