Usage
Fluorescein is primarily used as a diagnostic aid in ophthalmology and other medical fields. It is prescribed for:
- Fluorescein angiography: Examining the retinal and choroidal circulation for diagnosing conditions like diabetic retinopathy, macular degeneration, and retinal vascular occlusions.
- Fluorescein angioscopy: Visualizing the iris vasculature.
- Corneal staining: Detecting corneal abrasions, ulcers, and other injuries.
Pharmacological Classification: Diagnostic agent (dye).
Mechanism of Action: Fluorescein emits fluorescence when exposed to blue light, allowing visualization of blood vessels and other structures in the eye. It also stains damaged corneal and conjunctival tissues, making them readily apparent under appropriate lighting.
Alternate Names
- Fluorescein sodium
- Resorcinolphthalein
- D&C Yellow No. 7
Brand Names: Fluorescite, AK-Fluor, Fluorets.
How It Works
Pharmacodynamics: Fluorescein’s primary effect is the emission of fluorescence upon excitation with blue light. When administered intravenously, it rapidly distributes into the extracellular space, including the ocular vasculature. The dye’s fluorescence allows visualization of the retinal and choroidal circulation using specialized imaging techniques. Topically applied fluorescein stains damaged corneal and conjunctival epithelial cells, highlighting their location and extent.
Pharmacokinetics:
- Absorption: Intravenous administration leads to rapid distribution. Topical application results in minimal systemic absorption.
- Metabolism: Rapidly metabolized in the liver to fluorescein monoglucuronide, the primary metabolite.
- Elimination: Excreted primarily in the urine, with a small amount eliminated in bile. Urine fluorescence is typically observed for 24-36 hours post-administration.
Mode of Action: Fluorescein’s fluorescence is a physical property of the molecule and doesn’t involve receptor binding, enzyme inhibition, or neurotransmitter modulation. Its diagnostic utility stems from its ability to highlight vasculature and damaged tissues by contrasting their appearance against surrounding areas.
Dosage
Standard Dosage
Adults:
- Intravenous: 500 mg (5 mL of 10% solution or 2 mL of 25% solution) injected rapidly into the antecubital vein.
- Topical (ophthalmic): 1-2 drops of 0.5% or 2% solution instilled into the conjunctival sac.
Children:
- Intravenous: 7.7 mg/kg (up to a maximum of 500 mg) administered intravenously.
- Topical (ophthalmic): As per adult dosing.
Special Cases:
- Elderly Patients: No specific dosage adjustments are typically necessary.
- Patients with Renal Impairment: Dose reduction may be considered in patients with severe renal impairment or those undergoing dialysis. Some sources recommend halving the dose to 250mg for patients on dialysis.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are usually necessary.
- Patients with Comorbid Conditions: Caution is advised in patients with a history of allergies, especially to dyes.
Clinical Use Cases: Dosage is consistent with the standard recommendations for adults and children.
Dosage Adjustments: See special cases above.
Side Effects
Common Side Effects:
- Nausea and vomiting (IV)
- Transient yellow discoloration of skin and urine
- Strong taste in mouth (IV)
- Sneezing
- Local irritation and stinging (ophthalmic)
Rare but Serious Side Effects:
- Hypersensitivity reactions (including anaphylaxis)
- Cardiovascular events (e.g., hypotension, cardiac arrest)
- Neurological events (e.g., seizures)
Long-Term Effects: No significant long-term effects are typically associated with fluorescein use. Corneal opacification has been observed in rare cases with prolonged ophthalmic use.
Contraindications
- Hypersensitivity to fluorescein or any component of the formulation.
- Intrathecal or intra-arterial injection is contraindicated.
Drug Interactions
Fluorescein is generally considered inert and has few known drug interactions. However, caution is advised with:
- Beta-blockers: Concomitant use can potentially exacerbate hypersensitivity reactions.
- Organic anion transport inhibitors (e.g., probenecid): May alter the pharmacokinetics of fluorescein.
Interactions with laboratory tests: Fluorescein can interfere with certain laboratory tests, particularly those involving blood and urine analysis, for up to 3-4 days post-administration.
Pregnancy and Breastfeeding
- Pregnancy: Fluorescein is classified as Pregnancy Category C. Use only if clearly needed.
- Breastfeeding: Fluorescein is excreted in breast milk. Breastfeeding should be discontinued for at least 4 days following IV administration and discarded.
Drug Profile Summary
- Mechanism of Action: Fluorescent dye, visualizing vasculature and damaged tissues.
- Side Effects: Nausea, vomiting, discoloration of skin and urine, hypersensitivity reactions.
- Contraindications: Hypersensitivity.
- Drug Interactions: Beta-blockers, organic anion transport inhibitors.
- Pregnancy & Breastfeeding: Category C; excreted in breast milk.
- Dosage: Adults: 500 mg IV; Children: 7.7 mg/kg IV (max 500 mg). Ophthalmic: 1-2 drops.
- Monitoring Parameters: Observe for allergic reactions, especially during IV administration.
Popular Combinations: Fluorescein is typically used alone as a diagnostic agent.
Precautions
- General Precautions: Screen for allergies to fluorescein. Have emergency equipment available for managing potential hypersensitivity reactions during IV administration. Avoid extravasation during injection.
- Specific Populations: See Pregnancy and Breastfeeding section.
- Lifestyle Considerations: Temporary yellow discoloration of skin and urine may occur. Blurred vision and increased light sensitivity can follow angiography for up to 24 hours, affecting driving ability.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Fluorescein?
A: Adults: 500 mg IV. Children: 7.7 mg/kg IV (max 500 mg). Ophthalmic: 1-2 drops of 0.5-2% solution.
Q2: What are the most common side effects of fluorescein?
A: Nausea, vomiting, transient yellowing of skin and urine, and local irritation (ophthalmic).
Q3: What are the serious side effects of fluorescein?
A: Severe hypersensitivity reactions, including anaphylaxis, hypotension, and cardiac arrest.
Q4: Is fluorescein safe during pregnancy and breastfeeding?
A: Fluorescein is Pregnancy Category C; use only if clearly needed. Discontinue breastfeeding for at least 4 days following IV administration.
Q5: How is fluorescein administered for angiography?
A: It is administered as a rapid intravenous injection into the antecubital vein.
Q6: How is fluorescein administered for corneal staining?
A: It is applied topically as eye drops.
Q7: How does fluorescein work?
A: Fluorescein emits fluorescence when exposed to blue light, making certain structures visible.
Q8: What are the contraindications to fluorescein use?
A: Hypersensitivity to fluorescein. Intrathecal or intra-arterial injection is contraindicated.
Q9: How long does the skin discoloration last after fluorescein administration?
A: The yellowish discoloration of skin typically fades within 6-12 hours.
Q10: Does fluorescein interact with any medications?
A: Though rare, fluorescein can interact with beta-blockers and organic anion transport inhibitors. It can also interfere with some lab tests.
