fostamatinib

Contraindicated in:

OB: Pregnancy (may cause fetal harm);
Lactation: Lactation.

Use Cautiously in:

Hypertension;
Rep: Women of reproductive potential;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypertension, chest pain

Derm: rash

GI: diarrhea, nausea, ↑liver enzymes, abdominal pain, HEPATOTOXICITY

GU: ↓fertility (females)

Hemat: NEUTROPENIA

Neuro: dizziness, fatigue

Interactions ⬆ ⬇

Drug-drug:

Strong CYP3A4 inhibitors may ↑ levels of R406 and risk of toxicity;
Strong CYP3A4 inducers may ↓ levels of R406 and effectiveness; concurrent use not recommended;
May ↑ levels of CYP3A4 substrates;
May ↑ levels of BCRP substrates, including rosuvastatin;
May ↑ levels of P-glycoprotein substrates, including digoxin.

Availability ⬆ ⬇

Tablets: 100 mg; 150 mg

Route/Dosage ⬆ ⬇

PO (Adults ): 100 mg twice daily. After 1 mo, if platelet count has not ↑ to ≥50 × 10⁹/L, ↑ dose to 150 mg twice daily. Use lowest maintenance dose to maintain platelet count ≥50 × 10⁹/L. Discontinue after 12 wk if platelet count does not ↑ to level sufficient to prevent clinically relevant bleeding.

US Brand Names ⬆ ⬇

Action ⬆ ⬇

Acts as a tyrosine kinase inhibitor with activity against spleen tyrosine kinase. The major metabolite of fostamatinib, R406, reduces antibody-mediated destruction of platelets.

Therapeutic effects:

Increased platelet counts.

Classifications ⬆ ⬇

Therapeutic Classification: antithrombocytopenics

Pharmacologic Classification: kinase inhibitors

Pharmacokinetics ⬆ ⬇

Absorption: Prodrug that is converted to an active metabolite, R406; absolute bioavailability of R406 is 55%; absorption enhanced by high-calorie, high-fat foods.

Distribution: Extensively distributed to tissues.

Metabolism/Excretion: Metabolized in the gut by alkaline phosphatase to its major active metabolite, R406. R406 primarily metabolized in liver by CYP3A4 isoenzyme and through glucuronidation by UGT1A9. 80% of R406 excreted in feces, 20% in urine.

Half-Life: R406: 15 hr.

Time/Action Profile ⬆ ⬇

(plasma concentrations of R406)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	1–4 hr	unknown

Patient/Family Teaching ⬆ ⬇

Instruct patient to take fostamatinib as directed. If a dose is missed, omit and take next dose at scheduled time. Advise patient to read Patient Information before starting therapy and with each Rx refill in case of changes.
Inform patient of need to monitor BP during therapy. Advise patient to notify health care professional if signs and symptoms of hypertension (headaches, confusion, dizziness, chest pain, shortness of breath) occur.
Inform patient that diarrhea commonly occurs. Advise patient to treat with supportive measures and notify health care professional if diarrhea becomes severe.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Rep: May be teratogenic. Advise females of reproductive potential to use effective contraception and to avoid breastfeeding during and for at least 1 mo after last dose. May impair female fertility.
Emphasize importance of regular lab tests to monitor of effect and side effects.

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Indications ⬇

Contraind./Precautions ⬆ ⬇