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Chlorphentermine is a discontinued appetite suppressant, the para-chloro version of phentermine; adding a chlorine to the ring flips its character from a norepinephrine releaser toward a serotonin releaser, making it a less stimulating, more serotonergic anorectic. It was withdrawn because serotonergic appetite suppressants of its era turned out to damage heart valves and the lungs.
- The para-chloro version of phentermine
- A serotonergic appetite suppressant
- Less stimulating than phentermine
- Linked to heart-valve damage and pulmonary hypertension
Mechanism
Chlorphentermine is phentermine with a chlorine added to the aromatic ring, a small change that shifts it from releasing toward releasing (much like its relative fenfluramine). It suppresses appetite through that serotonergic signaling; the problem is that the same serotonin release stimulates 5-HT2B receptors on heart valves, which is the mechanism behind the valve disease and pulmonary hypertension seen with this drug class. It is also a classic research example of a drug that causes phospholipidosis (fatty accumulation in cells).
receptor fingerprint
release / transporter (SERT)releaser
5-HT2B receptorindirect agonism (via serotonin release)
transporter (NET)releaser
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
The serotonergic anorectics of this class are linked to heart-valve damage and pulmonary hypertension, which is exactly why chlorphentermine and its relatives were pulled from the market; it should never be combined with MAOIs or other serotonergic drugs (serotonin syndrome). It is a discontinued drug, not a current medicine. Not medical advice.
Subjective profileweighing the evidence above
Do not use it. It was pulled from the market because serotonergic appetite suppressants of its class damaged heart valves and caused pulmonary hypertension, and nothing about that has been revised. It is of historical interest only.
Resources
This entry is here for reference.
Research
- 1973first cited[Relation between serotonin metabolism and pulmonary hypertension in rats following administrat…
- 2006most recentDrug-induced phospholipidosis: issues and future directions.
- 1.Aminorex, fenfluramine, and chlorphentermine are serotonin transporter substrates. Implications for primary pulmonary hypertension.
- 2.[Relation between serotonin metabolism and pulmonary hypertension in rats following administration of various anorectic drugs]
- 3.Drug-induced phospholipidosis: issues and future directions.
3 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
How is chlorphentermine different from phentermine?
The added chlorine shifts it from a norepinephrine releaser (stimulating) to a serotonin releaser (calmer but riskier for the heart).
Why was it discontinued?
Serotonergic anorectics like it were tied to heart-valve disease and pulmonary hypertension via 5-HT2B stimulation.
Is it safe to use for weight loss?
No; it is discontinued and carries serious cardiopulmonary risks. This is historical/educational information only.
Adverse effects
- Linked to heart-valve damage and pulmonary hypertension
Notes and cautions
- Discontinued for safety reasons
- Serotonin-syndrome risk with MAOIs / serotonergics
- Causes cellular phospholipidosis