February 8, 2016
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Nascobal Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Nascobal Nasal Spray (cyanocobalamin) is used to treat vitamin B12 deficiency in people with pernicious anemia and other conditions. It is a man-made form of vitamin B12. Common side effects include headache, nausea, or runny nose.

The recommended initial dose of Nascobal Nasal Spray is one spray (500 mcg) administered in ONE nostril once weekly. Nascobal Nasal Spray may interact with antibiotics, methotrexate, pyrimethamine, colchicine, or alcohol. Tell your doctor all medications and supplements you use. During pregnancy, Nascobal Nasal Spray should be used only when prescribed. Based on information from related drugs, this medication may pass into breast milk. Consult your doctor before breastfeeding.

Our Nascobal Nasal Spray (cyanocobalamin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Nascobal in Detail - Patient Information: Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • chest pain;
  • feeling short of breath, even with mild exertion;
  • swelling, rapid weight gain; or
  • unusual warmth, redness, or pain in an arm or leg.

Less serious side effects may include:

  • headache, dizziness, weakness;
  • nausea, upset stomach, diarrhea;
  • numbness or tingling;
  • runny nose, sneezing, sore throat, swollen tongue;
  • fever;
  • joint pain; or
  • itching or rash.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Nascobal (Cyanocobalamin)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Nascobal Overview - Patient Information: Side Effects

SIDE EFFECTS: Headache, nausea, or runny nose may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication may cause low potassium levels in the blood (hypokalemia). Tell your doctor immediately if any of these unlikely but serious side effects occur: muscle cramps, weakness, irregular heartbeat.

People who have a rare blood disorder (polycythemia vera) may infrequently have symptoms related to this disorder while taking cyanocobalamin. Seek immediate medical attention if any of these rare but very serious symptoms occur: chest pain (especially with shortness of breath), weakness on one side of the body, sudden vision changes, slurred speech.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Nascobal (Cyanocobalamin)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Nascobal FDA Prescribing Information: Side Effects
(Adverse Reactions)


The incidence of adverse experiences described in the Table below are based on data from a short-term clinical trial in vitamin B12 deficient patients in hematologic remission receiving Nascobal (Cyanocobalamin, USP) Gel for Intranasal Administration (N=24) and intramuscular vitamin B12 (N=25). In the pharmacokinetic study comparing Nascobal (cyanocobalamin) Nasal Spray and Nascobal (cyanocobalamin) Nasal Gel, the incidence of adverse events was similar.

Table. Adverse Experiences by Body System, Number of Patients and Number of Occurrences by Treatment Following Intramuscular and Intranasal Administration of Cyanocobalamin.

    Number of Patients (Occurrences)
Body System Adverse Experience Vitamin B12
Nasal Gel,
500 mcg
Vitamin B12 ,
100 mcg
Body as a Whole Asthenia 1 (1) 4 (4)
Back Pain 0 (0) 1 (1)
Generalized Pain 0 (0) 2 (3)
Headache 1 (2)* 5 (11)
Infectiona 3 (4) 3 (3)
Cardiovascular System Peripheral Vascular Disorder 0 (0) 1 (1)
Digestive System Dyspepsia 0 (0) 1 (2)
Glossitis 1 (1) 0 (0)
Nausea 1 (1)* 1 (1)
Nausea & Vomiting 0 (0) 1 (1)
Vomiting 0 (0) 1 (1)
MusculoskeletalSystem Arthritis 0 (0) 2 (2)
Myalgia 0 (0) 1 (1)
Nervous System Abnormal Gait 0 (0) 1 (1)
Anxiety 0 (0) 1 (1)*
Dizziness 0 (0) 3 (3)
Hypoesthesia 0 (0) 1 (1)
Incoordination 0 (0) 1 (2)*
Nervousness 0 (0) 1 (3)*
Paresthesia 1 (1) 1 (1)
Respiratory Dyspnea 0 (0) 1 (1)
System Rhinitis 1 (1)* 2 (2)
a Sore throat, common cold
* There may be a possible relationship between these adverse experiences and the study drugs. These adverse experiences could have also been produced by the patient's clinical state or other concomitant therapy.

The intensity of the reported adverse experiences following the administration of Nascobal (Cyanocobalamin, USP) Gel for Intranasal Administration and intramuscular vitamin B12 were generally mild. One patient reported severe headache following intramuscular dosing. Similarly, a few adverse experiences of moderate intensity were reported following intramuscular dosing (two headaches and rhinitis; one dyspepsia, arthritis, and dizziness), and dosing with Nascobal (Cyanocobalamin, USP) Gel for Intranasal Administration (one headache, infection, and paresthesia).

The majority of the reported adverse experiences following dosing with Nascobal (Cyanocobalamin, USP) Gel for Intranasal Administration and intramuscular vitamin B12 were judged to be intercurrent events. For the other reported adverse experiences, the relationship to study drug was judged as “possible” or “remote”. Of the adverse experiences judged to be of “possible” relationship to the study drug, anxiety, incoordination, and nervousness were reported following intramuscular vitamin B12 and headache, nausea, and rhinitis were reported following dosing with Nascobal (Cyanocobalamin, USP) Gel for Intranasal Administration.

The following adverse reactions have been reported with parenteral vitamin B12:

Generalized: Anaphylactic shock and death (See WARNINGS and PRECAUTIONS).

Cardiovascular: Pulmonary edema and congestive heart failure early in treatment; peripheral vascular thrombosis.

Hematological: Polycythemia vera.

Gastrointestinal: Mild transient diarrhea.

Dermatological: Itching; transitory exanthema.

Miscellaneous: Feeling of swelling of the entire body.

Read the entire FDA prescribing information for Nascobal (Cyanocobalamin)

Nascobal - User Reviews

Nascobal User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Nascobal sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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