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I recently moved to US. It's been 7 to 8 days. I feel general kind of weakness, sometimes, not every time. I was taking paroxetine while I was back in India. Right now, I'm not taking it. And I had minor bleeding episodes, one in the gums and one after defecation. It was not a large quantity of blood but fresh blood was present. I am feeling cold here.. its cold but usually i take less time to adapt to climate but its difficult for me right now.

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paroxetine discontinuation syndrome symptoms

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Now I have comprehensive information to give a thorough, well-sourced answer.

What's Likely Happening to You

This picture - weakness, bleeding episodes, and poor cold adaptation after 7-8 days of stopping paroxetine - fits together well under one main explanation, with a few things worth checking.

1. Paroxetine Discontinuation Syndrome (Most Likely Primary Cause)

Paroxetine is the antidepressant most commonly associated with withdrawal/discontinuation syndrome. This is not a minor issue - textbook data from Maudsley Deprescribing Guidelines shows that abrupt discontinuation of paroxetine produced a withdrawal syndrome in 66-100% of patients in double-blind RCTs, with a mean of 7-10 withdrawal symptoms per patient.
Why paroxetine specifically? It has a short half-life (~21 hours), and it is a potent inhibitor of its own metabolizing enzyme (CYP2D6 - autoinhibition). When you stop it abruptly, plasma levels drop very steeply, faster than most other antidepressants. The Maudsley Deprescribing Guidelines note that paroxetine had "a stronger signal for risk of withdrawal than the opioid buprenorphine" in the WHO adverse effect database.
Symptoms of paroxetine discontinuation syndrome include (Rosen's Emergency Medicine):
  • General somatic symptoms - weakness, fatigue, lethargy, anorexia (fits your weakness)
  • Disequilibrium - dizziness, ataxia
  • Sleep disturbances
  • Gastrointestinal symptoms - nausea, diarrhea
  • Sensory symptoms - "electric shock" sensations, paresthesias
  • Affective symptoms - irritability, anxiety
Your generalized, intermittent weakness fits solidly into the somatic category of this syndrome. It typically starts within the first 3 days of stopping but can persist for weeks, especially after longer use.

2. The Bleeding Episodes - Directly Related to Paroxetine (a Paradox Worth Understanding)

This is important: the bleeding you experienced - gum bleeding and fresh blood after defecation - is consistent with being on paroxetine, not with stopping it. Here's why:
SSRIs (and paroxetine is among the strongest serotonin reuptake inhibitors) deplete platelet serotonin. Serotonin is normally released from platelets at sites of vascular injury to promote vasoconstriction and clot formation. By chronically blocking serotonin uptake into platelets, SSRIs reduce the platelet's ability to form clots, increasing bleeding risk.
From Maudsley Prescribing Guidelines:
"The relative risk of any bleeding event on an SSRI/SNRI compared with no use is 1.4, with the absolute risk being between 0.5% and 6%."
Paroxetine specifically (along with sertraline and fluoxetine) is classified as a strong serotonin reuptake inhibitor - the category with the highest bleeding risk.
The lower GI bleeding (rectal) had a hazard ratio of 2.96 in population-based studies for SSRI users. Fresh blood after defecation could represent:
  • Minor ano-rectal source (hemorrhoids, anal fissure) made more noticeable due to SSRI-related platelet dysfunction
  • Lower GI mucosal source
The gum bleeding fits the same platelet mechanism.
The timing (7-8 days after stopping) suggests this bleeding may have begun while you were still on paroxetine or immediately after stopping before the platelet serotonin stores fully normalize.
What to watch for: If these bleeding episodes continue, increase, or are accompanied by larger volumes of blood, you need medical evaluation promptly. A single small episode that has not recurred may resolve on its own.

3. Cold Intolerance and Slow Climate Adaptation

Cold intolerance that feels disproportionate has several possible contributors here:
  • Discontinuation syndrome itself - autonomic instability and dysregulation of thermoregulation are recognized features. Serotonin plays a role in thermoregulation, and abrupt loss of serotonergic tone can impair the body's thermal set-point temporarily.
  • General debility - the weakness and fatigue from discontinuation reduce physical activity, which reduces heat generation.
  • Worth considering: if you had any prior thyroid issues (cold intolerance + weakness + fatigue can also be hypothyroidism), that is worth ruling out with a simple blood test (TSH).

What You Should Do

Short term (this week):
  1. See a doctor or urgent care clinic - explain that you were on paroxetine and stopped abruptly after relocating. Ask about restarting at your previous dose and then tapering slowly. According to the Maudsley Guidelines, a proper taper involves very gradual, hyperbolic dose reductions - often over weeks to months, not days.
  2. Mention the bleeding episodes to the doctor. Small, self-limited bleeding after stopping an SSRI is consistent with what is known, but fresh rectal blood always warrants clinical evaluation to rule out a structural cause.
If you restart paroxetine: Discontinuation symptoms typically resolve within 24-48 hours of restarting the medication at your previous dose.
Proper tapering: When you do eventually stop paroxetine, taper by no more than 5-10mg every 2-4 weeks. Clinical trial data showed tapering this way reduced the withdrawal rate from 33.8% (abrupt stop) to just 4.6%.

Red Flags - Seek Immediate Care If:

  • Bleeding becomes heavier or more frequent
  • You notice blood in vomit or black/tarry stools (suggests upper GI bleed)
  • Severe dizziness, fainting, or difficulty walking
  • High fever or severe agitation (these would suggest something other than discontinuation)
References:
Disclaimer: This is educational information based on published medical literature, not a clinical diagnosis or treatment prescription. Please see a licensed physician in the US - a primary care doctor or urgent care clinic can help you manage this safely.

So decrease in serotonin can cause bleeding and paroxetine is an SSRI, so if I stopped it, there is a general reduction in serotonin, right?

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Good question, but the logic has a common mix-up in it. Here is the correct chain of events:

The Mechanism is About Platelets, Not Systemic Serotonin

Paroxetine does NOT reduce the total amount of serotonin in your body. It blocks a transporter (SERT - the serotonin transporter) that pumps serotonin into cells for storage or re-use.
Here is what actually happens, step by step:
While you ARE on paroxetine:
  1. Platelets normally use SERT to absorb and store serotonin from the bloodstream
  2. Paroxetine blocks SERT - so platelets cannot load up on serotonin
  3. Over days/weeks, platelets become depleted of serotonin
  4. When a blood vessel is injured, platelets release serotonin to cause vasoconstriction and aggregation - but they have very little to release
  5. Result: impaired clot formation → increased bleeding risk
The serotonin is not "destroyed" - it stays in the blood/brain. But the platelets specifically cannot store it.
When you STOP paroxetine:
  1. The SERT block is lifted
  2. Platelets gradually start re-absorbing and re-stocking serotonin
  3. Bleeding risk should normalize over days to weeks

So Where Does Your Bleeding Fit?

Your bleeding episodes at 7-8 days likely represent a carry-over effect. Platelets have a lifespan of about 8-10 days. The platelets circulating when you stopped paroxetine were already serotonin-depleted. New platelets being produced now will gradually replace them with full serotonin stores, but that takes roughly the same 8-10 days.
So at day 7-8 of stopping, you are right at the edge of the transition window - your old depleted platelets are still circulating, but fresh ones are coming online.

The Brain Side is Different

For mood and discontinuation symptoms, the story IS about relative serotonin signaling - but not because total serotonin drops. It is because:
  • Your brain adapted over time to having SERT blocked (it adjusted receptor sensitivity, receptor numbers, etc.)
  • When paroxetine is removed abruptly, the system is suddenly under-compensated - there is a functional drop in serotonergic tone even though serotonin molecules are still present
  • The brain has not had time to readjust its receptor landscape
This is why discontinuation symptoms (weakness, dizziness, "brain zaps") feel like serotonin withdrawal - because functionally, they are - just not through the mechanism of "less serotonin being made."
In short: The bleeding was caused by being on paroxetine (platelet SERT blockade), and should resolve now that you have stopped. The weakness and cold intolerance are from the brain adapting to the sudden removal of SERT blockade. Two different mechanisms, both from the same drug, at different ends of the timeline.
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