Primidone
Commercial names and formulations:
Brand name: Mysoline
Formulations: Tablets and syrup
Years on the market:
Since 1954 in the US
How to store it?
Store at room temperature
What does the body do to the medication?
Can I take it with food?
Yes
How long does it take to get to the blood after I take it?
3 hours in adults and 4 to 6 hours in children
How long does it take to start having a steady effect?
2-3 days
Can this medication be started at a high dose or it has to be started gradually?
Gradually
How long does it stay in the body?
About ½ day
How is it eliminated?
About one quarter of primidone is converted by the liver into Phenobarbital. The liver is responsible for the metabolism of the parent and its metabolites
What does the medication do to the body?
Type of epilepsy that helps:
Partial Epilepsy
FDA approved for:
Partial onset seizures with and without secondarily generalized seizures
Common side effects:
• Skin: rash
• Bones: none
• Blood: decrease in granulocytes (reduces ability to fight off infection), anemia
• Liver: none
• Kidneys: none
• Stomach and intestines: nausea, anorexia, vomiting
• Heart: none
• Brain: difficulty with coordination, dizziness, drowsiness
• Mood: hyperirritability, emotional disturbances, anxiety, depression
• Others: fatigue, sexual impotency, double vision, involuntary eye movements
Serious side effects:
Unusual bruising or bleeding
Frequent infections
Risk of suicidal thoughts or behavior
What happens if I get too much of it (intoxication)?
Symptoms can include drowsiness or fatigue, slurred speech, coordination problems, paranoia, difficulty breathing, rapid heart rate, low blood pressure, and sweating. Coma and death can also occur.
What happens if I stop it suddenly (withdrawal)?
Primidone should be stopped gradually. Sudden withdrawal of Primidone may cause an increase in seizures or status epilepticus.
Who should not take this medication?
You should not take primidone if you are allergic to the medication Phenobarbital or have acute intermittent porphyria.
What is the average dose and how many times a day should be given?
Children: 125-250 mg (taken 3 times a day) or approximately 10-25 mg/kg/day
Adults: 125-250 mg (taken 3 or 4 times a day) or approximately 20 mg/kg/day
Does the body get used to the medication?
Yes
Medications to be careful with:
Other AEDs that may increase the blood level of primidone:
None anticipated
Other AEDs that may decrease the blood level of primidone:
Phenytoin, Carbamazepine
Other drug interactions:
Primidone (via its metabolite Phenobarbital) will lower levels of felbamate, carbamazepine, lamotrigine, topiramate, tiagabine, zonisamide, lorazepam, and diazepam, and valproic acid.
Isonazid inhibits the conversion of primidone to Phenobarbital and may cause side effects.
Primidone lowers levels of estrogen, steroids, warfarin.
Blood work required?
CBC and CPM?
Complete Blood Count
How often?
Every 3-6 months initially
Are medication levels in blood useful?
Yes
Normal range
3-12 mcg/mL
Women’s health
Affects contraceptives?
Yes
Affect fertility?
Yes
Are safe in pregnancy?
Primidone may cause certain birth defects. Discuss with your doctor.
Category
Pregnancy Category D
Can breastfeed?
Primidone is passed through breast milk so it may or may not be safe to breast feed while taking it. The multiple benefits of breastfeeding need to be weighed against the probable small, but unknown, risks of the baby getting the medication. The amount the baby will get will not be possible to predict or measure. The baby needs to be watched closely for excessive sleepiness and poor feeding.
Affect bones (osteoporosis)?
Yes
Men’s health
Affects sexual performance?
Sexual impotency
Affects fertility?
Some reports have associated this class of medication with decreased sperm counts
Use other than epilepsy:
Essential tremor and psychiatric conditions