Usage
- Selenious Acid Injection is prescribed as a source of selenium for patients receiving total parenteral nutrition (TPN) when oral or enteral nutrition isn’t feasible, insufficient, or contraindicated. This applies to both adult and pediatric patients. It helps maintain plasma selenium levels and prevents deficiency symptoms.
- Pharmacological classification: Trace element, nutritional supplement.
- Mechanism of Action: Selenious acid is converted to selenide in the body, which is then incorporated into selenoproteins. These proteins have crucial roles as antioxidants, protecting cells from damage. A key selenoprotein is glutathione peroxidase, which neutralizes harmful free radicals.
Alternate Names
- Selenium dioxide monohydrate
- There are no widely recognized international variations. Brand names include Selenious Acid Injection, USP. A specific brand, Selenomax, exists for the oral form of selenium. Another brand name is Selepen for the oral form.
How It Works
- Pharmacodynamics: Selenium is an essential trace element and a component of selenoproteins, which act as antioxidants, especially glutathione peroxidase. This enzyme reduces oxidative stress by catalyzing the reduction of hydrogen peroxide and lipid peroxides, protecting cells from damage. Selenium also has roles in thyroid hormone metabolism and immune function.
- Pharmacokinetics:
- Absorption: Administered intravenously as part of TPN solutions, bypassing absorption.
- Metabolism: Converted to selenide and incorporated into selenoproteins.
- Elimination: Primarily excreted in urine, also in feces, lungs, and skin.
- Mode of action: Acts as a cofactor for glutathione peroxidase, facilitating its antioxidant activity. It also helps maintain the heart and blood vessels, and keeps the heart muscle and skin tissue healthy. It may also help treat and prevent cancer.
- Receptor binding, enzyme inhibition, or neurotransmitter modulation: Primarily acts as a cofactor rather than through receptor binding, enzyme inhibition, or neurotransmitter modulation. Elimination pathways are mainly renal excretion, and to some extent through feces, lungs, and skin. Metabolism involves incorporation into selenoproteins, and excess selenium may be methylated and eliminated.
Dosage
Standard Dosage
Adults:
- 60 mcg/day added to TPN solution. Higher dosages may be necessary based on clinical needs.
Children:
- Less than 7 kg: 2 to 4 mcg/kg/day added to TPN solution.
- 7 kg and above: 2 mcg/kg/day added to TPN solution (up to 60 mcg/day).
- Pediatric safety considerations include careful monitoring of selenium levels and avoiding exceeding the recommended dose. A 6 mcg/mL concentration is recommended for pediatric use, particularly those weighing 7 kg or less, to ensure accurate dosing.
Special Cases:
- Elderly Patients: Dose adjustments are generally not required but individualize based on the patient’s clinical condition and nutritional status.
- Patients with Renal Impairment: Consider careful monitoring as selenium is primarily excreted renally. Dose adjustments may be necessary depending on the degree of impairment.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are indicated, but clinical monitoring is advised.
- Patients with Comorbid Conditions: No formal recommendations exist, monitor based on patient response and consider comorbid conditions influencing nutritional needs.
Clinical Use Cases
Selenious acid is specifically indicated for use in TPN and isn’t independently dosed in the following clinical scenarios:
- Intubation
- Surgical Procedures
- Mechanical Ventilation
- Intensive Care Unit (ICU) Use
- Emergency Situations
Dosage Adjustments
Adjustments should be based on the patient’s clinical condition, nutritional requirements, selenium levels, and any oral or enteral intake.
Side Effects
Common Side Effects
No selenium-related adverse reactions have been reported within the recommended dosage range when administered intravenously as part of TPN.
Rare but Serious Side Effects
Pulmonary embolism due to pulmonary vascular precipitates is a rare but serious side effect. If signs of pulmonary distress occur, stop the infusion and initiate a medical evaluation.
Long-Term Effects
Chronic selenosis (selenium toxicity) can manifest as garlic breath, hair loss, nail changes, and gastrointestinal issues. This is more associated with chronic high oral intake and is unlikely to be observed with appropriate IV dosing in TPN.
Adverse Drug Reactions (ADR)
Pulmonary embolism caused by precipitate formation. Discontinue the infusion immediately if pulmonary distress occurs.
Contraindications
None known for Selenious Acid Injection when used as directed in TPN. However, it is contraindicated for direct intravenous infusion without proper dilution.
Drug Interactions
- Medications affecting selenium levels (e.g., cisplatin, corticosteroids, valproic acid).
- Anticoagulants/Antiplatelet drugs (e.g., warfarin, clopidogrel, heparin, aspirin): May increase bleeding risk.
- Immunosuppressants: May decrease their effectiveness.
- Various other drugs may impact selenium excretion rates, either increasing (e.g., amiloride, chlorothiazide) or decreasing (e.g., alogliptin, alprazolam, amantadine) them. These interactions require monitoring and potential dosage adjustment.
- Several medications can interact with selenium, such as those listed in the Drug Interactions section.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C. Although administration of the recommended dose in parenteral nutrition is not expected to cause adverse fetal outcomes, selenium at high doses can be teratogenic in animals. Use during pregnancy only if the potential benefit justifies the potential risk. Selenium is present in the placenta and umbilical cord blood.
- Breastfeeding: Selenium is present in human milk. The recommended dosage for lactating women is 70 mcg/day, and the approved recommended dose in PN is not expected to harm the infant. However, no data exists on the effects of selenious acid on milk production. Consider both the benefits of breastfeeding and potential infant risk.
Drug Profile Summary
- Mechanism of Action: Antioxidant via incorporation into selenoproteins like glutathione peroxidase.
- Side Effects: Generally well-tolerated at recommended doses in TPN. Rare: pulmonary embolism.
- Contraindications: None when used as directed in TPN.
- Drug Interactions: Various; see drug interactions section.
- Pregnancy & Breastfeeding: Category C; use with caution. Selenium is present in breast milk.
- Dosage: Adults: 60 mcg/day. Pediatrics: weight-based (see above).
- Monitoring Parameters: Selenium levels, electrolyte balance, renal and hepatic function, signs of pulmonary distress.
Popular Combinations
Selenious acid is typically included in TPN formulations with other essential trace elements, vitamins, amino acids, dextrose, and lipids as needed. Specific combinations vary based on individual patient requirements.
Precautions
- General Precautions: Monitor selenium levels and observe for signs of toxicity or pulmonary distress. Always dilute before IV administration. Adhere to proper admixture procedures.
- Specific Populations: See dosage section for elderly, renal/hepatic dysfunction patients. Consult with specialist before administering to pregnant women or breastfeeding mothers, balancing the benefits and risks.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Selenious acid in TPN?
A: Adults: 60 mcg/day. Pediatrics: Less than 7 kg: 2 to 4 mcg/kg/day; 7 kg and above: 2 mcg/kg/day (up to 60 mcg/day).
Q2: How is Selenious Acid Injection administered?
A: It should only be administered after dilution in a TPN solution. It is not for direct IV infusion.
Q3: What is the role of selenium in the body?
A: Selenium is essential for the function of selenoproteins, particularly glutathione peroxidase, a key antioxidant enzyme.
Q4: What are the signs of selenium toxicity?
A: Garlic breath, hair loss, nail changes, gastrointestinal disorders, and nervous system effects. With intravenous administration, pulmonary embolism is a rare but serious concern.
Q5: Can pregnant or breastfeeding women receive Selenious Acid Injection?
A: It’s a Pregnancy Category C drug, meaning caution is advised. Consult with a specialist to weigh the risks and benefits. Selenium is present in breast milk.
Q6: Are there any clinically significant drug interactions with selenious acid?
A: Yes, several drugs can interact, impacting selenium levels or increasing bleeding risk (e.g., warfarin). See the Drug Interactions section for details.
Q7: How should I monitor patients receiving Selenious Acid Injection?
A: Closely monitor selenium blood levels, fluid and electrolytes, renal and liver function tests, and observe for signs of pulmonary distress.
Q8: What should I do if a patient exhibits signs of pulmonary distress during Selenious Acid infusion?
A: Immediately discontinue the infusion and initiate a medical evaluation for potential pulmonary embolism.
Q9: Is Selenious Acid compatible with other components of TPN solutions?
A: Generally, yes, it’s physically compatible with electrolytes and other trace elements typically included in TPN. However, always check for precipitate formation and emulsion stability after admixing.
