Primidone: Difference between revisions
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MDElliottMD (talk | contribs) Category taxonomy ship: retag Anticonvulsants -> Antiepileptics, Sedative-Hypnotics -> Sedative-hypnotics |
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{{MedTemplate | {{MedTemplate | ||
| generic | | generic = Primidone | ||
| brand | | brand = Mysoline | ||
| structure | | structure = | ||
| classes | | classes = [[:Category:Anticonvulsants|Anticonvulsant]], [[:Category:Barbiturates|Barbiturate (parent compound)]], [[:Category:Tremor medicines|Tremor medicine]] | ||
| | | uses = <vote slug="partial-seizures-monotherapy-use">Partial-onset and generalized tonic-clonic seizures (FDA)</vote>, <vote slug="essential-tremor-use">Essential tremor (widely used and AAN-guideline-supported as first-line alongside propranolol)</vote> | ||
| uses | | starting_dose = Seizures: 100-125 mg PO at bedtime x 3 days, then BID, then TID, escalating to 750-1500 mg/day. Essential tremor: 25-50 mg PO at bedtime, titrate slowly to 250-750 mg/day | ||
| starting_dose | | preparations = Tablets 50, 250 mg | ||
| preparations | | fda_max = 2 g/day (seizures); typically much lower for essential tremor | ||
| fda_max = | | pill_id = | ||
| routes | | routes = Oral | ||
| onset | | onset = Anticonvulsant effect emerges with slow titration over weeks; tremor effect over weeks | ||
| duration | | duration = BID-TID dosing | ||
| halflife | | halflife = Primidone 5-15 hours; '''phenobarbital active metabolite 50-150 hours'''; PEMA (phenylethylmalonamide) active metabolite 16 hours<ref name="mysoline-label">FDA Prescribing Information, Mysoline (primidone), Bausch/various, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2010/009170s032lbl.pdf</ref> | ||
| bioavailability = ~90% (oral)<ref name="mysoline-label" /> | |||
| pregnancy = Substantial teratogenic signal (barbiturate class effects including neonatal withdrawal and hemorrhagic disease of newborn).{{citation needed}} | |||
| legal = [[USLegal:Prescription only|Rx-only]] in US. '''Federally non-controlled despite being a barbiturate''', a paradoxical situation given that its primary active metabolite phenobarbital is Schedule IV<ref name="mysoline-label" /> | |||
| | | mechanism = <vote slug="primidone-mech-claim">Barbiturate that metabolizes to two active species: '''phenobarbital''' (the major contributor to seizure control, mediating GABA-A receptor potentiation) and '''PEMA (phenylethylmalonamide)''', which contributes to seizure control and is the leading candidate to explain the essential-tremor efficacy. Phenobarbital alone does not reliably suppress tremor at non-sedating doses, so PEMA's independent action is the proposed mechanism for the tremor indication.</vote> Strong CYP3A4 induction via the phenobarbital metabolite produces many interactions (reduces oral contraceptives, warfarin, many psychotropics). Essential-tremor efficacy is the unique pharmacological selling point<ref name="mysoline-label" />. | ||
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== References == | |||
<references /> | |||
[[Category:Anticonvulsants]] | |||
[[Category:Barbiturates]] | [[Category:Barbiturates]] | ||
[[Category: | [[Category:Tremor medicines]] | ||