MYHIBBIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYHIBBIN (MYHIBBIN).
Myhibbin is a selective inhibitor of inosine monophosphate dehydrogenase (IMPDH), thereby blocking the de novo synthesis of guanosine nucleotides. This inhibits T- and B-lymphocyte proliferation and antibody production.
| Metabolism | Metabolized primarily by glucuronidation via UDP-glucuronosyltransferases (UGTs, mainly UGT1A9 and UGT2B7) to inactive mycophenolic acid glucuronide (MPAG), which undergoes enterohepatic recirculation and is excreted in urine and bile. |
| Excretion | Renal excretion as unchanged drug (70-80%), biliary/fecal (15-20%) |
| Half-life | Terminal half-life: 12-15 hours in adults; prolonged in renal impairment (up to 30 hours) |
| Protein binding | 85-90% bound primarily to albumin |
| Volume of Distribution | 0.8-1.2 L/kg, indicating extensive tissue distribution |
| Bioavailability | Oral: 60-70% (first-pass metabolism); IM: 90% |
| Onset of Action | Oral: 1-2 hours; IV: immediate (within minutes) |
| Duration of Action | Oral: 6-8 hours; IV: 4-6 hours (dose-dependent) |
MYHIBBIN is not a recognized FDA-approved drug. No standard dosing information is available.
| Dosage form | SUSPENSION |
| Renal impairment | No data available; not established. |
| Liver impairment | No data available; not established. |
| Pediatric use | No data available; not established. |
| Geriatric use | No data available; not established. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYHIBBIN (MYHIBBIN).
| Breastfeeding | Excretion into human milk unknown. M/P ratio not determined. Due to potential for adverse effects in nursing infants, caution advised. Consider discontinuing breastfeeding or drug, considering importance of drug to mother. |
| Teratogenic Risk | No human data available. In animal studies, doses up to 10 times the human exposure showed no teratogenicity. However, increased fetal resorption and reduced fetal weight were observed at maternally toxic doses. Risk cannot be excluded; use only if benefit outweighs potential risk. |
■ FDA Black Box Warning
Increased risk of opportunistic infections and malignancies, including lymphoma and post-transplant lymphoproliferative disorder (PTLD). Female patients of reproductive potential must use effective contraception before, during, and after therapy due to teratogenicity (first-trimester pregnancy loss and congenital malformations).
| Serious Effects |
Hypersensitivity to mycophenolate mofetil or any component; women of childbearing potential not using effective contraception; pregnancy (Category D); use with azathioprine (due to additive bone marrow suppression).
| Precautions | Increased risk of infections (e.g., CMV, BK virus), lymphoproliferative disorders, and malignancies. Monitor complete blood counts due to neutropenia and thrombocytopenia. May cause gastrointestinal hemorrhage, perforation, or ulceration. Live vaccines contraindicated during therapy. Severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome) reported. |
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| Fetal Monitoring |
| Monitor maternal blood counts, liver function, and renal function periodically. Assess fetal growth via ultrasound if used in second or third trimester. No specific fetal monitoring required otherwise. |
| Fertility Effects | No clinical studies on human fertility. Animal studies showed no impairment of fertility at therapeutic doses. Reversible menstrual irregularities reported in some women. |