Methemoglobin is a form of hemoglobin (HEEM o glo bin). Hemoglobin is a substance in blood that carries oxygen and distributes it to your tissues and organs. However, methemoglobin is not a type of hemoglobin that is useful in carrying oxygen.

Methemoglobin normally exists in small amounts in the blood. However, when methemoglobin levels increase, the blood is less efficient in circulating oxygen. The resulting lack of oxygen throughout the body can cause symptoms such as pale or blue-colored skin.

Methemoglobinemia is a condition in which methemoglobin is present in high levels in the blood. Methemoglobinemia can occur when a person is exposed to certain drugs or chemicals such as nitrites.

Methylene blue injection is used to treat methemoglobinemia. This medicine works by converting methemoglobin to a more efficient type of hemoglobin to better carry oxygen throughout the body.

Methylene blue may also be used for purposes not listed in this medication guide.

You should not be treated with methylene blue if you are allergic to it, or if you have:

• a genetic enzyme deficiency called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Many drugs can interact with methylene blue. Tell your doctor about all your current medicines and any you recently stopped using, especially:

• alfentanil, fentanyl;
• buspirone;
• digoxin, digitalis;
• dihydroergotamine, ergotamine;
• phenytoin;
• pimozide;
• quinidine;
• warfarin (Coumadin, Jantoven);
• an MAO inhibitor--isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, tranylcypromine, and others;
• an "SSRI" antidepressant--citalopram, escitalopram, fluoxetine, paroxetine, sertraline, Prozac, Paxil, Zoloft, and others;
• an "SNRI" antidepressant--desvenlafaxine, duloxetine, levomilnacipran, milnacipran, venlafaxine, Effexor, Cymbalta, Pristiq, and others;
• other antidepressants--bupropion, clomipramine, mirtazapine; or
• medicine to prevent organ transplant rejection--cyclosporine, sirolimus, tacrolimus.

To make sure methylene blue is safe for you, tell your doctor if you have:

• liver disease; or
• kidney disease.

Using methylene blue during pregnancy could harm the unborn baby. Tell your doctor if you are pregnant.

Do not breast-feed within 8 days after you received methylene blue. If you use a breast pump during this time, throw out any milk you collect. Do not feed it to your baby.

Use Methylene Blue (Provayblue) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

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

Tell your caregivers right away if you have:

• confusion or weakness;
• pale or yellowed skin;
• dark colored urine;
• fever; or
• high levels of serotonin in the body--agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting.

Common side effects may include:

• pain in your arms or legs;
• blue or green urine;
• altered sense of taste;
• headache, dizziness;
• sweating, skin discoloration;
• nausea; or
• feeling hot.

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.

This medicine may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

For at least 24 hours after treatment with methylene blue, avoid exposure to sunlight or tanning beds. This medicine can make you sunburn more easily. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.