Summary
Pethidine is significantly less safe than other opioids due to its toxic metabolite norpethidine, which accumulates with repeated dosing and can cause seizures, tremors, and CNS excitation. It should not be used for more than 48 hours or at doses exceeding 600 mg per 24 hours. The drug has a particularly high risk of serotonin syndrome compared to other opioids and should never be combined with MAOIs, SSRIs, or other serotonergic drugs. Intravenous administration carries extreme risks and should only be done in medical settings with naloxone and respiratory support immediately available. Norpethidine accumulation is especially dangerous in patients with renal impairment.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 50-100mg | 100-200mg | 200-400mg | 400mg+ |
| Intramuscular | 25-50mg | - | - | - |
| Intravenous | 25-50mg | - | - | 100+mg(extremecaution-rapidrespiratorydepression)+ |
| Subcutaneous | 25-50mg | - | - | - |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Peak | Offset | After Effects | Total |
|---|---|---|---|---|---|
| Oral | 30-60 min | 1-2 hrs | 2-4 hrs | 2-10 hrs | 240-0 min |
| Intramuscular | 10-15 min | 30-60 min | 1-2 hrs | 1-6 hrs | 240-0 min |
| Intravenous | 1-5 min | 5-10 min | 1-2 hrs | 1-6 hrs | 240-0 min |
| Subcutaneous | 10-20 min | 30-60 min | 1-2 hrs | 1-6 hrs | 240-0 min |
Tolerance
Build-up
develops within days of regular use; analgesic tolerance faster than respiratory depression tolerance
Reset
7–14 days for partial reset; full reset may take weeks — tolerance loss greatly increases overdose risk
Effects
Positive
- Physical Euphoria
- Pain Relief
- Stimulation
- Cough Suppression
- Analgesia
Negative
- Respiratory Depression
- Nausea
- Seizures
- Dry Mouth
- Sedation
- Itchiness
- Pupil Constriction
- Difficulty Urinating
- Relaxant
Positive
- Cognitive Euphoria
- Anxiety Suppression
- Dream Potentiation
- Euphoria
- Mood lift
- Cognitive euphoria
- Anxiety suppression
Negative
- Constipation
- Compulsive Redosing
- Time distortion
Positive
- Increased libido
Negative
- Acuity Suppression
- Decreased Libido
- Appetite Suppression
- Orgasm Suppression
- Appetite suppression
- Dehydration
- Light sensitivity
- Disinhibition
- Dulled perception