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Fenethylline is a prodrug that links an amphetamine molecule to theophylline (a caffeine-like xanthine). Once in the body it splits back into amphetamine plus theophylline, so its effects are mostly those of amphetamine with an added xanthine stimulant kick. It was originally a prescription stimulant and later became infamous under the brand name Captagon.
- Wakefulness and energy
- Reduced fatigue
- Appetite suppression
- Insomnia and anxiety
- Raised heart rate and blood pressure
- Dependence potential
- Psychosis with heavy use
Mechanism
On its own fenethylline is inactive; the body metabolizes it into amphetamine and theophylline. The amphetamine portion drives release of and (and blocks their reuptake), producing classic stimulant effects, while the theophylline adds a milder xanthine stimulation and bronchodilation. Because it releases the amphetamine gradually, its onset was historically described as somewhat gentler than amphetamine itself.
receptor fingerprint
()Releasing agent (via amphetamine)
transporter (NET)Releasing agent (via amphetamine)
receptorsAntagonist (via theophylline)
Safetyrisks and cautions, not medical advice
Its risks are essentially those of amphetamine plus a xanthine: raised heart rate and blood pressure, insomnia, anxiety, appetite loss, and with heavy use psychosis and cardiovascular strain. Dependence and compulsive redosing are real concerns. Combining it with MAOIs or other stimulants is dangerous for blood pressure and serotonin balance. Not medical advice.
Subjective profileweighing the evidence above
Effectively a slow-release amphetamine with a caffeine-like passenger, so it inherits amphetamine's dependence, psychosis and cardiovascular risks without offering anything amphetamine does not. Its modern life is as a black-market stimulant, and there is no reason to seek it out.
Resources
This entry is here for reference.
Research
- 1.Fenetylline: new results on pharmacology, metabolism and kinetics.
- 2.Captagon: use and trade in the Middle East.
2 listed here; entry last updated July 2026
Reviews
My notesprivate to this device
FAQ
Why is fenethylline called a prodrug?
It is inactive until the body breaks it into amphetamine and theophylline, which are the parts that actually cause the effects.
Is it the same as Captagon?
Captagon was the original brand name for fenethylline, though many modern street "Captagon" tablets contain plain amphetamine or other stimulants instead.
Is it addictive?
Yes, because it delivers amphetamine, it carries amphetamine's potential for dependence and compulsive use.
Adverse effects
- Insomnia and anxiety
- Raised heart rate and blood pressure
- Dependence potential
- Psychosis with heavy use