Glycerol Phenylbutyrate
Mechanism :
It's a triglyceride that contains 3 molecules of phenylbutyrate. It serves as an alternative vehicle for waste nitrogen excretion, which helps to reduce blood ammonia and glutamine concentrations in patients with certain urea cycle disorders.
Indication :
- Hyperammonemia in patients with urea cycle disorders.
Contraindications :
hypersensitivity, Breastfeeding not recommended, caution in renal, hepatic, pancreatic impairment
Dosing :
For patients changing from Na phenylbutyrate tablets: Total daily oral dose (mL) = total daily dose of Na phenylbutyrate in gm x 0.86.
For patients changing from Na phenylbutyrate powder: Total daily oral dose (mL) = total daily dose of Na phenylbutyrate in gm x 0.81.
Divide total daily dosage into 3 doses and round each dose to nearest 0.1 mL. Max daily dose: 17.5 ml/ 19 gm.
Patients who are phenylbutyrate naive:
4.5 to 11.2 mL/m2/day PO divided in three equal doses, each rounded to the nearest 0.5 mL in children more than 2 years old, and up to the nearest 0.1 ml in children less than 2 years.
Adverse Effect :
diarrhoea, flatulence, headache, low neurtrophils, fever, decreased appetite, cough, rash
Interaction :
Anti epileptics: valproate, ethosuximide, carbamazepine
Benzodiazapines: triazolam, midazolam
Steroids: prednisone, prednisolone, triamcinolone acetonide, methylprednisolone, hydrocortisone, fludrocortisone, cortisone, dexamethasone, betamethasone
Steroid sparing: tacrolimus, sirolimus, everolimus, cyclosporine
Antipsychotics: haloperidol, pimozide
Opiod: fentanyl, alfentanil
Ergot derivatives: ergotamine, dihydroergotamine
quinine, quinidine
anti- gout: probenecid, colchicine
disopyramide
clonidine
Hepatic Dose :
Moderate to severe hepatic impairment: Use a lower starting dose