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% and avoid very large single doses
DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
CAPD                :Dialysed. 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      :Not dialysed. Dose as in GFR=10–20 mL/min
IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugs
Antibacterials: reduced concentration of chloramphenicol, doxycycline, metronidazole, telithromycin and possibly rifampicin – avoid with telithromycin
Anticoagulants: increased metabolism of coumarins (reduced effect)
Antidepressants: antagonise anticonvulsant effect; reduces concentration of paroxetine, mianserin and tricyclics; concentration reduced by St John’s wort – avoid concomitant use
Antifungals: possibly reduced concentration of itraconazole, posaconazole and voriconazole – avoid concomitant use with voriconazole; reduced absorption of griseofulvin (reduced effect)
Antipsychotics: antagonise anticonvulsant effect; metabolism of haloperidol increased; possibly reduces aripiprazole concentration – increase aripiprazole dose; concentration of both drugs reduced with chlorpromazine
Antivirals: concentration of abacavir, amprenavir, darunavir, indinavir, lopinavir, nelfinavir and saquinavir possibly reduced
Calcium-channel blockers: effect of felodipine, isradipine and probably dihydropyridines, diltiazem and verapamil reduced
Diuretics: concentration of eplerenone reduced – avoid concomitant use; increased risk of osteomalacia with carbonic anhydrase inhibitorsOestrogens and progestogens: metabolism accelerated, reduced contraceptive effectSodium oxybate: enhanced effects of sodium oxybate – avoid
Tacrolimus: concentration of tacrolimus reduced
ADMINISTRATION
Reconstition
–
Route
IV, oral
Rate of Administration
Not more than 100 mg/minute
Comments
For IV administration, dilute 1 in 10 with water for injectionPhenobarbital (phenobarbitone).578 PhEnoBArBiTAL (PhEnoBArBiTonE)
OTHER INFORMATION
Aim for plasma concentration of 15– 40 mg/L (65–170 µmol/L) for optimum responseMay cause excessive sedation and increased osteomalacia in ERFCharcoal haemoperfusion and haemodialysis more effective than peritoneal dialysis for poisoningUp to 50% unchanged drug excreted in urine with alkaline diuresis.
