Drug Interactions between pemigatinib and tacrolimus topical

Pemigatinib may be taken with or without food. Do not consume grapefruit, grapefruit juice, or any supplements that contain grapefruit extract during treatment with pemigatinib unless directed otherwise by your doctor. Grapefruit juice can increase the blood levels of pemigatinib. This may increase the frequency and severity of serious side effects such as elevated phosphate levels in the blood (which can eventually lead to low blood calcium levels; calcium deposits in the skin, muscles, and other tissues; anemia; muscle cramps; seizures; and irregular heart rhythm), eye and vision problems, joint pain, mouth sores and inflammation, hair loss, diarrhea, nausea, vomiting, and constipation. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

The use of calcineurin inhibitors as pimecrolimus and tacrolimus topical should be avoided in immunocompromised adults and children, including patients on systemic immunosuppressive medications. Although causal relationship has not been established, there is a concern about a potential risk of infections, lymphomas and skin malignancies when using topical calcineurin inhibitors for a prolonged time.

The recommended dosage of pemigatinib should be reduced in patients with severe hepatic dysfunction. No dose adjustment is recommended for patients with mild or moderate hepatic impairment.

Rare postmarketing cases of acute renal failure have been reported in patients treated with topical tacrolimus. Systemic absorption is most likely to occur in patients with epidermal barrier defects, and when topical tacrolimus is applied to large body surface areas. Caution should be exercised in patients with history of renal impairment or predisposed to renal impairment.

The recommended dosage of pemigatinib should be reduced in patients with severe renal disease. No dose adjustment is recommended for patients with mild or moderate renal impairment, or those patients with end-stage renal disease receiving intermittent hemodialysis.

The use of calcineurin inhibitors such as pimecrolimus and tacrolimus topical should be avoided on malignant or premalignant skin conditions. Some of these conditions might present as dermatitis. Calcineurin inhibitors should also be avoided in any skin conditions where there is the potential for increased systemic absorption of the medication as when there is a skin barrier defect.

Pemigatinib can cause retinal pigment epithelial detachment (RPED), which may cause symptoms such as blurred vision, visual floaters, or photopsia. A comprehensive ophthalmological examination including an optical coherence tomography should be performed prior to treatment initiation. Patients with visual disturbances should be closely monitored.