Phenobarbital
Aliases: Pheno, Luminal, Solfoton, Phenobarb, Phenobarbitone
Categories
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. Medical supervision is essential for discontinuation due to life-threatening withdrawal risks. Largely replaced by safer alternatives but still used for refractory epilepsy and neonatal seizures.
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 | After Effects |
|---|---|---|---|---|---|
| Oral | 15-60 min | 1-2 hrs | 4-6 hrs | 12-24 hrs | 1-48 hrs |
| Intravenous | 5 min | - | 15-30 min | 12-24 hrs | 1-48 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
Effects
Positive
- Muscle relaxation
- Physical euphoria
- Physical Euphoria
- Muscle Relaxation
- Pain Relief
- Anxiolysis
Negative
- Respiratory depression
- Motor impairment
- Ataxia
- Sedation
Positive
- Anxiety suppression
- Cognitive euphoria
Negative
- Motor control loss
- Amnesia
- Thought deceleration
- Analysis suppression
- Emotion suppression
- Language suppression
- Dizziness
- Compulsive redosing
- Delusions of sobriety
Positive
- Increased Music Appreciation
- Tactile Enhancement
- Color enhancement
Negative
- Disinhibition
- Acuity suppression
- Decreased Libido
- Acuity Suppression
- Dehydration
- Light sensitivity
- Dulled perception