Vitamin B-12 (cyanocobalamin (vitamin B-12))

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Cyanocobalamin is administered by IM or deep subcutaneous injection. Cyanocobalamin also is administered orally and intranasally. Hydroxocobalamin is administered by IM injection or IV infusion. Oral therapy with vitamin B12 preparations is markedly inferior to parenteral therapy and should be used only for the treatment of dietary vitamin B12 deficiency in patients with normal GI absorption.

No dosing information is available for this tab.

No dosing information is available for this tab.

Safety of concomitant administration of other cyanide antidotes with hydroxocobalamin (Cyanokit(R)) has not been established. Caution is advised if another cyanide antidote is administered to patients receiving hydroxocobalamin.

Absorption of vitamin B12 from the GI tract may be decreased by aminoglycoside antibiotics, colchicine, extended-release potassium preparations, aminosalicylic acid and its salts, anticonvulsants (e.g., phenytoin, phenobarbital, primidone), cobalt irradiation of the small bowel, and by excessive alcohol intake lasting longer than 2 weeks. Neomycin-induced malabsorption of vitamin B12 may be increased by concurrent administration of colchicine.

Ascorbic acid may destroy substantial amounts of dietary vitamin B12 in vitro; this possibility should be considered when large doses of ascorbic acid are ingested within 1 hour of oral vitamin B12 administration.

Prednisone has been reported to increase the absorption of vitamin B12 and secretion of IF in a few patients with pernicious anemia, but not in patients with partial or total gastrectomy. The clinical importance of these findings is unknown.

Concurrent administration of chloramphenicol and vitamin B12 reportedly may antagonize the hematopoietic response to vitamin B12 in vitamin B12-deficient patients. The hematologic response to vitamin B12 in patients receiving both drugs should be carefully monitored and alternate anti-infectives should be considered.

There are no contraindication interactions for this drug.

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Folic Acid/Fluorouracil & Fluorouracil Prodrugs

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Folic acid has been shown to enhance both the therapeutic and toxic effects of fluoropyrimidines, such as 5-fluorouracil (5-FU) and fluorouracil prodrugs.(1-3) Fluorouracil prodrugs include capecitabine and tegafur.

CLINICAL EFFECTS: Folic acid, when used concurrently with 5-FU or fluorouracil prodrugs, has been shown to increase side effects of 5-FU.(1-3)

PREDISPOSING FACTORS: Patients who are intermediate or poor dihydropyrimidine dehydrogenase (DPYD) metabolizers have diminished or no DPYD function. Since DPYD is the rate-limiting enzyme involved in fluoropyrimidine metabolism, these patients may be more susceptible to the effects of this interaction.(3)

PATIENT MANAGEMENT: Folic acid or folate analog-containing products should not be used concurrently with fluorouracil or fluorouracil prodrugs unless directed by the healthcare provider.(1-3) Fluorouracil prodrugs include capecitabine and tegafur.

DISCUSSION: Due to increased toxic effects, stomatitis and diarrhea are observed more commonly, may be more severe, and may occur for a prolonged duration when compared to therapy with 5-FU alone. It is postulated that the lower standard dose of 5-FU in the US versus other regions may be due to increased folic acid supplementation within the US food supply.(2) In a cohort study in 290 patients, the use of dietary supplements with folic acid during treatment compared to nonuse increased the risk of capecitabine toxicities (HR 1.81, 95%CI: 1.15,2.85). The detection of folic acid in plasma also increased the risk of capecitabine toxicities (HR 2.09, 95%CI: 1.24,3.52 and HR 2.31, 95%CI: 1.29,4.13 at diagnosis and during treatment, respectively).(4) In a cohort study of 9 patients, patients taking folate-containing supplements and higher serum folate levels had an increased risk of grade >=2 toxicity. The risk of grade >=2 toxicity increased by 9% for every increase in serum folate level by 10 nmol/L. Patients with grade >=2 toxicity had higher serum folate levels than patients with grade <= 1 toxicity (28 nmol/L [range, 13.2-45.4] vs. 20 nmol/L [range, 12.8-45.4]; p=0.001).(5) In two case reports, patients developed capecitabine toxicity while taking supplements containing folic acid 400-500 mcg.(6) In a case report, a woman developed grade 4 diarrhea, grade 3 vomiting, and grade 3 hand-foot syndrome 8 days after the addition of capecitabine (2500 mg/m2/day) to high-dose folic acid supplementation. She developed necrotic colitis and died, despite the discontinuation of folic acid and capecitabine.(7) There are two other reports of excessive fluorouracil toxicity in patients treated with folic acid.(8)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Folic Acid/Pafolacianine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Folate, folic acid, and folate-containing supplements may reduce binding of pafolacianine to folate receptors expressed on ovarian cancer cells.

CLINICAL EFFECTS: Folate, folic acid, and folate-containing supplements could reduce the detection of malignant lesions with pafolacianine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid administration of folate, folic acid, or folate-containing supplements within 48 hours before administration of pafolacianine.

DISCUSSION: Folate, folic acid, and folate-containing supplements may reduce binding of pafolacianine to folate receptors expressed on cancer cells, which could result in reduced detection of malignant lesions with pafolacianine.

There is no enhanced messaging for this drug.

• Leber's hereditary optic atrophy

There are no severe contraindications for this drug.

• Atrophic gastritis
• Hypokalemia

There is no enhanced messaging for this drug.

There are no severe adverse reactions for this drug.

Less Frequent

• Diarrhea
• Pruritus of skin

No enhanced messaging available.

No enhanced messaging available.

Adequate and well-controlled studies have not been conducted in pregnant women. However, vitamin B12 requirements are increased in pregnant women. Parenteral preparations should be used during pregnancy only when the potential benefits justify the potential risks to the fetus.

Vitamin B12 is distributed into human milk. Vitamin B12 requirements are increased in lactating women.

Hydroxocobalamin may be administered to lactating women with suspected or known cyanocobalamin poisoning. There is no data available to determine when breastfeeding may be restarted following administration of IV hydroxocobalamin.

No enhanced messaging available.