20 to 50     : Dose as in normal renal function
10 to 20     : Dose as in normal renal function, but avoid very large doses
<10           : Reduce dose by 25–50% initially, and avoid very large single doses
DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
CAPD                :Unknown dialysability. Dose as in GFR <10 mL/min
HD                     :Dialysed. Dose as in GFR
<10           : mL/min
HDF/high flux   :Dialysed. Dose as in GFR
<10           : mL/min
CAV/VVHD      :Dialysed. Dose as in GFR=10–20 mL/min
IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugs
Antibacterials: reduced concentrations of chloramphenicol, doxycycline, metronidazole and telithromycin
Anticoagulants: increased metabolism of coumarins (reduced effect)
Antidepressants: antagonise anticonvulsant effect; reduces concentration of paroxetine, mianserin and tricyclics; St John’s wort reduces active primidone metabolite concentration – avoid concomitant use
Anti-epileptics: reduces concentration of carbamazepine; carbamazepine reduces primidone concentration but increases metabolite concentration; possibly reduces concentration of ethosuximide; reduces concentration of lamotrigine and tiagabine; primidone concentration possibly reduced by phenytoin, but active metabolite increased and concentration of phenytoin may be altered; primidone concentration possibly increased by valproate, valproate concentration reduced; concentration of primidone possibly reduced by vigabatrin
Antifungals: possibly reduces concentration of posaconazole and voriconazole – avoid concomitant use; reduces absorption of griseofulvin (reduced effect)
Antimalarials: possibly increased risk of convulsions with chloroquine and hydroxychloroquine; anticonvulsant effect antagonised by mefloquine
Antivirals: concentration of indinavir, lopinavir, nelfinavir and saquinavir possibly reduced
Calcium-channel blockers: effect of felodipine, isradipine and probably other dihydropyridines, diltiazem and verapamil reduced
Ciclosporin: reduces ciclosporin blood levelsCorticosteroids: metabolism of corticosteroids accelerated, reduced effectOestrogens and progestogens: metabolism accelerated, reduced contraceptive effect
ADMINISTRATION
Reconstition
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Route
Oral
Rate of Administration
–
Comments
–.PriMidonE 605
OTHER INFORMATION
Plasma concentrations of 5–12 mcg/L (23– 55 µmol/L) have been loosely correlated with optimum responsePartially converted to phenobarbital and phenylethylmalonamide with long half-lives (metabolites may accumulate in renal impairment)May cause excessive sedation and osteomalacia.