Myfenax

Uses

Prophylaxis of organ rejection in kidney transplant: Myfenax is used for the prophylaxis of organ rejection in adult patients receiving a kidney transplant. It is used for the prophylaxis of organ rejection in pediatric patients 5 years of age and older who are at least 6 months post kidney transplant.

Myfenax is also used to associated treatment for these conditions: Kidney Transplant Rejection

How Myfenax works

Myfenax is a potent, selective, uncompetitive, and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), and therefore inhibits the de novo pathway of guanosine nucleotide synthesis without incorporation into DNA. Because T- and B-lymphocytes are critically dependent for their proliferation on de novo synthesis of purines, whereas other cell types can utilize salvage pathways, mycophenolic acid has potent cytostatic effects on lymphocytes. Myfenax inhibits proliferative responses of T- and B-lymphocytes to both mitogenic and allospecific stimulation. Addition of guanosine or deoxyguanosine reverses the cytostatic effects of mycophenolic acid on lymphocytes. Myfenax also suppresses antibody formation by B-lymphocytes. Myfenax prevents the glycosylation of lymphocyte and monocyte glycoproteins that are involved in intercellular adhesion to endothelial cells and may inhibit recruitment of leukocytes into sites of inflammation and graft rejection.

Dosage

Myfenax dosage

Dosage in adult kidney transplant patients: The recommended dose of Myfenax is 720 mg administered twice daily (1440 mg total daily dose).

Dosage in pediatric kidney transplant patients: The recommended dose of Myfenax in conversion (at least 6 months post-transplant) pediatric patients age 5 years and older is 400 mg/m2 body surface area (BSA) administered twice daily (up to a maximum dose of 720 mg administered twice daily). Pediatric patients with a BSA of 1.19 to 1.58 m2 may be dosed either with three Myfenax 180 mg tablets, or one 180 mg tablet plus one 360 mg tablet twice daily (1080 mg daily dose). Patients with a BSA of >1.58 m2 may be dosed either with four Myfenax 180 mg tablets, or two Myfenax 360 mg tablets twice daily (1440 mg daily dose).

Myfenax tablets should be taken on an empty stomach, 1 hour before or 2 hours after food intake. Tablets should not be crushed, chewed, or cut prior to ingesting. The tablets should be swallowed whole in order to maintain the integrity of the enteric coating.

Side Effects

The most common adverse reactions (≥20%) associated with the administration of Myfenax are anemia, leukopenia, constipation, diarrhea, vomiting, dyspepsia, urinary tract infection, CMV infection, insomnia, and postoperative pain.

Toxicity

Oral (LD50): Acute: 352 mg/kg [Rat], 1000 mg/kg [Mouse], and >6000 mg/kg Rabbit. Possible signs and symptoms of acute overdose could include the following: hematological abnormalities such as leukopenia and neutropenia, and gastrointestinal symptoms such as abdominal pain, diarrhea, nausea and vomiting, and dyspepsia.

Precaution

Myfenax tablets are used with caution because it-

• Can cause embryofetal toxicity
• Can increase new or reactive viral infections
• Can cause blood dyscrasias including pure red cell aplasia
• Can cause serious GI tract complications (gastrointestinal bleeding, perforations and ulcers)
• May increase the risk of developing lymphomas and other malignancies, particularly of the skin
• Use of live vaccine should be avoided during treatment with Myfenax

Interaction

Caution should be exercised with concomitant administration of Antacids, Azathioprine, Cyclosporin, Rifampin, Sevelamer, Cholestyramine, Acyclovir, Metronidazole, Hormonal contraceptives as these medicines may decrease Myfenax concentration.

Food Interaction

• Take on an empty stomach. Take mycophenolic acid at least 1 hour before or 2 hours after eating.

Volume of Distribution

• 54 ± 25 L

Elimination Route

Bioavailability following oral administration of Myfortic delayed-release tablet ranges from 70-95%

Half Life

The mean elimination half-life for mycophenolic acid ranges from 8-16 hours, while that of the MPAG metabolite ranges from 13-17 hours.

Clearance

• 140 +/- 30 mL/min [Stable renal transplant patients]

Pregnancy & Breastfeeding use

Pregnancy Category D. Can cause fetal harm.

Lactation: Discontinue Myfenax or discontinue nursing while on treatment or within 6 weeks after stopping therapy. Take into consideration the importance of the drug to the mother.

Contraindication

Myfenax delayed-release tablets and Mycophenolate mofetil tablets and capsules should not be used interchangeably without physician supervision because the rate of absorption following the administration of these two products is not equivalent.

Acute Overdose

No data are available with regard to overdose.

Storage Condition

Store at 25° C and Keep out of reach of children.

Innovators Monograph

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