256 mg of phenobarbital taken with water on empty stomach (5rs out from a light meal) (3 x 64 mg pills) & (2 x 32 mg pills) I made sure to wait for the effects to start setting in before I cooked and ate a small cheese pizza, so as to ensure the drug made its way into the system unimpeded.
Phenobarbital
Well-documented
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 17 combo interactions documented
- PubChem toxicity data
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 17 combo interactions documented
- PubChem toxicity data
Aliases: Pheno, Luminal, Solfoton, Phenobarb, Phenobarbitone
Summary
Phenobarbital is a long-acting barbiturate with extremely slow elimination and a narrow therapeutic window. It binds to a distinct allosteric site on GABA-A receptors separate from benzodiazepines, making combinations particularly dangerous as effects potentiate multiplicatively. Tolerance develops rapidly but not to lethal doses, narrowing the safety margin.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 50-100mg | 100-150mg | 150-300mg | 300mg+ |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset |
|---|---|---|---|---|
| Oral | 15-60 min | 1-2 hrs | 4-6 hrs | 12-24 hrs |
| Intravenous | 5 min | - | 15-30 min | 12-24 hrs |
Tolerance
Build-up
develops over 1–4 weeks of daily use; hypnotic tolerance faster than anxiolytic tolerance
Reset
weeks to months depending on half-life and duration of use; taper recommended
Tolerance Decay
Full tolerance
14d
Half tolerance
14d
Baseline
~60d
Acute tolerance: develops within a single session — the reset numbers above apply after sustained heavy use, not after one binge. Within-session tachyphylaxis usually resets largely overnight.
Tolerance to sedative effects typically builds with regular daily use over 1–2+ weeks and decays slowly over several weeks; data are largely clinical experience and user reports rather than controlled studies. Cross-tolerance with other positive GABAA modulators (e.g., benzodiazepines) is partial but clinically relevant. Because of phenobarbital’s long half-life, perceived tolerance may reflect accumulation rather than receptor-level changes.
Cross-Tolerances
Other barbiturates
100%
Benzodiazepines
50%
Effects
Aggregated from 4 Erowid experience reports
Positive Effects 1
Anxiety Suppression
100.0%
70%
Adverse Effects 0
Combinations
Cross-Check Phenobarbital with another substanceCommunity Trip Reports
Anecdotal first-person accounts from Reddit, Erowid, and Bluelight. Click a source to expand. Reports are harm-reduction context, not medical guidance.
Erowid 4 reports 1 neutral 3 cautionary visit
First, let me note I am typing this from a BlackBerry about 50 minutes post dose. Also, I have a professional education in biology, chemistry, and health care practice, allowing inherent extreme familiarity with the substance(s) involved in terms of pharmacokinetics, pharmacology, and contraindications as well as recom...
My son woke up to a seizure five days ago. Although febrile seizures typically last only five or so minutes, his lasted possibly over an hour. At the hospital he received a rectal injection of Ativan (dosage unknown) which failed to stop the seizure which then prompted a 'loading dose' of phenobarbital (dosage unknown)...
I'd like to just my experiences with a certain drug called Phenobarbital. I'm a sixteen year old with an extensive trip history over the past year or so (marijuana, acid, psilocybes, amanitas, dimenhydrinate), but when I tried the drug I was an inexperienced fifteen year-old.
Pill Identifiers
35
known pill identifiers on record — view imprints, colors, shapes, and images
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Phenobarbital's nerd page
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Helpful Links
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