Phenobarbital
Also sold as: Luminal, Gardenal
Prescription neededEpilepsy and nerve pain
Comes as:TabletSyrupInjection
Usual adult dose
Usual adult dose for epilepsy: 60 mg to 180 mg once a day at night, set by your doctor. Children: dose by weight — ask your doctor. Do not stop it suddenly.
Your doctor may give you a different dose. Children's doses depend on weight.
Side effects
Common
- drowsiness
- slowed thinking
- unsteady walking
- overactivity or irritability in children
Serious — get help
Stop taking it and see a doctor straight away if you notice:
- slow breathing
- severe skin rash
- severe confusion
- dependence
Do not take it, or take care, if
- Severe breathing problems
- Porphyria
- Severe liver disease
- Use with alcohol or other sedatives
- Pregnancy (ask your doctor)
Interactions
Medicines that can react with this one.
Serious3 medicinesDo not take these together unless your doctor says so.
- Diazepam
Together they can cause deep sedation and slowed breathing.
- Ethinylestradiol + Levonorgestrel
Phenobarbital makes the contraceptive pill less effective; use another method.
- Warfarin
Phenobarbital lowers the effect of warfarin; INR must be checked.
Moderate1 medicineTake together only with care. Ask your doctor or pharmacist.
- Sodium valproate
Valproate raises phenobarbital levels and drowsiness.
Minor1 medicineUsually not a problem, but tell your doctor.
- Montelukast
Phenobarbital can lower montelukast levels and reduce its effect.