selenium

Selenium is an essential trace element that is required in minute quantities to maintain good health. The human body does not produce selenium and it must be obtained from dietary intake. Selenium is taken as a supplement by people with selenium deficiency. Selenium is available over the counter (OTC) as tablets and capsules and is also administered as an intravenous (IV) injection for patients who cannot take it orally.

Selenium deficiency can affect many systems in the body including the cardiovascular system, muscles and joints, and cognitive health. Selenium is a constituent of several important proteins and enzymes known as selenoproteins which are essential for DNA synthesis, growth and reproduction, thyroid hormone metabolism, immune system function and antioxidant activity. Selenium is present as selenocysteine amino acid in selenoprotiens. Some important selenoproteins include:

• Glutathione peroxidase, a family of antioxidant enzymes that neutralize reactive oxygen and nitrogen species (free radicals) and protect tissues from oxidative damage that these unstable molecules cause.
• Iodothyronine deiodinase, a group of enzymes that activate and deactivate thyroid hormones.
• Thioredoxin reductase, an enzyme that helps form reduced thioredoxin, which serves as a source of electrons for enzymes involved in DNA synthesis.

Selenium is present in soil in most places. Major dietary sources of selenium include Brazil nuts, fish, shellfish, poultry, beef, turkey, eggs, beans, dairy, green vegetables, mushrooms, brown rice, and fortified cereals. Selenium has a narrow therapeutic window, however, and excessive use of selenium supplements can be toxic.

• Selenium injection is not for direct intravenous use. It should be admixed with other nutrients prepared for intravenous (parenteral) administration, as per directions.
• Use selenium with caution in patients with gastrointestinal or kidney function impairment.
• Intravenous administration of selenium carries a risk for vein damage, and blood clot blocks (thrombosis) in the blood vessels and in the lungs (pulmonary embolism). Monitor the patient for symptoms.
• Selenium injection contains aluminum that can reach toxic levels in preterm infants because of immature kidneys, and in patients with kidney function impairment. Monitor such patients closely.
• Monitor patient’s levels of selenium, electrolytes, blood glucose, blood count and clotting parameters, and liver and kidney function during treatment with selenium.

Selenium taken in recommended doses does not have any known side effects. Prolonged use with high doses can cause side effects including:

• Hair loss (alopecia)
• Brittle nails
• Skin rash
• Garlic breath odor
• Gastrointestinal disturbances
• Fatigue
• Irritability
• Tingling and numbness (paresthesia)
• Impairment of speech, balance and coordination (ataxia)

Rare side effects of selenium intravenous injections include:

• Vein damage and blood clot block (thrombosis)
• Blood clot in lungs (pulmonary embolism)
• Aluminum toxicity from aluminum in the injection solution

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Tablet

• 50 mcg
• 100 mcg
• 125 mcg
• 200 mcg

Tablet extended release

• 200 mcg

Capsule

• 200 mcg

Injectable solution

• 40 mcg/mL

Adult:

Recommended Daily Allowance (RDA)

• Male or female: 55 mcg/day
• Pregnancy: 60 mcg/day
• Lactating: 70 mcg/day

Supplementation

• 100-200 mcg/day orally with meals (preferably); may take 50 mcg orally once daily or once every 6 hours

Pediatric:

RDA

• Children below 6 months: 15 mcg/day
• Children 6-12 months: 20 mcg/day
• Children 1-3 years: 20 mcg/day
• Children 4-8 years: 30 mcg/day
• Children 8-13 years: 40 mcg/day
• Children 13-18 years: 55 mcg/day

Overdose

• Acute mild to moderate selenium overdose can cause symptoms such as irritability, muscle pain and muscle spasms, while symptoms of severe overdose can include nausea, vomiting, diarrhea, abdominal pain, garlic breath odor, altered mental status, and circulatory collapse that can be fatal.
• Prolonged overuse of selenium can cause selenosis, with symptoms that include hair loss (alopecia), brittle nails, skin rash, garlic breath, gastrointestinal disturbances, fatigue, irritability, tingling and numbness (paresthesia), and impairment of speech, balance and coordination (ataxia).
• Selenium does not have any known antidote. Overdose is treated with symptomatic and supportive care.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Selenium has no known severe interactions with other drugs.
• Serious interactions of selenium include:
  • baloxavir marboxil
  • eltrombopag
• Moderate interactions of selenium include:
  • alendronate
  • bictegravir
  • deferiprone
  • dolutegravir
  • eltrombopag
  • etidronate
  • ibandronate
  • omadacycline
  • penicillamine
  • raltegravir
  • risedronate
  • tiludronate
  • trientine
• Selenium has no known mild interactions with other drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• Selenium is a trace metal that is important for good health. Requirement of trace elements, including selenium, increases during pregnancy. Deficiency in trace elements is associated with adverse pregnancy and fetal outcomes. 
• The necessary RDA of selenium is best obtained from dietary intake, however, taking recommended doses of selenium supplements during pregnancy to prevent deficiency is acceptable.
• Selenium is present in breastmilk. No adverse events have been observed with recommended doses of selenium. Use with caution if you are a nursing mother.
• Do not take any OTC products, including selenium, without first checking with your healthcare provider, if you are pregnant or breastfeeding.

• Take selenium exactly as prescribed. Do not exceed the recommended daily allowance because selenium, though an essential element, can be toxic in excess.
• Selenium can be easily obtained in a wide variety of food sources. Avoid taking selenium supplements unless you are diagnosed with deficiency and advised by your physician, although selenium supplements are available OTC.
• Store selenium safely out of reach of children.
• In case of overdose, seek medical help or contact Poison Control.