Fluorescein is a synthetic organic photoactive dye molecule that dissolves in water, alcohol, and solvents [1].

Absorption, Distribution and Excretion
Rapidly distributed
Fluorescein and its metabolites are mainly eliminated via renal excretion.
0.5 L/kg
renal cl=1.75 mL/min/kg [After IV administration]
hepatic cl=1.50 mL/min/kg [After IV administration]
Fluorescence of skin persists for several hr, and dye appears in urine for as long as 30 hr.
Within 7 to 14 seconds after IV administration into antecubital vein, fluorescein usually appears in the central artery of the eye. Within a few minutes of IV administration of fluorescein sodium, a yellowish discoloration of the skin occurs, which begins to fade after 6 to 12 hours of dosing. Various estimates of volume of distribution indicate that fluorescein distributes well into interstitial space (0.5 L/ kg).
Fluorescein and its metabolites are mainly eliminated via renal excretion. After IV administration, the urine remains slightly fluorescent for 24 to 36 hours. A renal clearance of 1.75 mL/min/kg and a hepatic clearance (due to conjugation) of 1.50 mL/min/kg have been estimated. The systemic clearance of fluorescein was essentially complete by 48 to 72 hours after administration of 500 mg fluorescein.
Fluorescein sodium has been demonstrated to be excreted in human milk.
The permeability of the blood-retinal and blood-aqueous barriers to fluorescein and the rate of aqueous flow can be estimated by measurements of fluorescein in the vitreous, aqueous, and plasma after systemic administration. Fluorescein is commonly measured by fluorescence, but fluorescein glucuronide, a metabolite of fluorescein, also fluoresces. To assess the influence of fluorescein glucuronide on the quantitation of fluorescein by fluorescence, we studied the pharmacokinetics of fluorescein and fluorescein glucuronide for 38 hr in the plasma of five normal subjects given 14 mg/kg of sodium fluorescein intravenously. The plasma and the plasma ultrafiltrate were measured by fluorescence and by high performance liquid chromatography. In our fluorophotometer, fluorescein glucuronide was 0.124 times as fluorescent as fluorescein. Fluorescein was rapidly converted to fluorescein glucuronide, and within 10 min the concentration of unbound fluorescein glucuronide exceeded that of unbound fluorescein. The terminal half-lives of fluorescein and fluorescein glucuronide in the plasma ultrafiltrate were 23.5 and 264 min, respectively, so that fluorescein glucuronide contributed almost all of the plasma fluorescence after 4-5 hr. Because fluorescein glucuronide was less bound in the plasma than fluorescein, the ratio of the fluorescence of the plasma ultrafiltrate to that of the plasma increased with time. The greatest proportion of the total fluorescein available to penetrate into the ocular compartments occurred shortly after injection. ...

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Metabolism / Metabolites
The permeability of the blood-retinal and blood-aqueous barriers to fluorescein and the rate of aqueous flow can be estimated by measurements of fluorescein in the vitreous, aqueous, and plasma after systemic administration. Fluorescein is commonly measured by fluorescence, but fluorescein glucuronide, a metabolite of fluorescein, also fluoresces. To assess the influence of fluorescein glucuronide on the quantitation of fluorescein by fluorescence, we studied the pharmacokinetics of fluorescein and fluorescein glucuronide for 38 hr in the plasma of five normal subjects given 14 mg/kg of sodium fluorescein intravenously. The plasma and the plasma ultrafiltrate were measured by fluorescence and by high performance liquid chromatography. In our fluorophotometer, fluorescein glucuronide was 0.124 times as fluorescent as fluorescein. Fluorescein was rapidly converted to fluorescein glucuronide, and within 10 min the concentration of unbound fluorescein glucuronide exceeded that of unbound fluorescein. The terminal half-lives of fluorescein and fluorescein glucuronide in the plasma ultrafiltrate were 23.5 and 264 min, respectively, so that fluorescein glucuronide contributed almost all of the plasma fluorescence after 4-5 hr. Because fluorescein glucuronide was less bound in the plasma than fluorescein, the ratio of the fluorescence of the plasma ultrafiltrate to that of the plasma increased with time. The greatest proportion of the total fluorescein available to penetrate into the ocular compartments occurred shortly after injection. ...
Fluorescein undergoes rapid metabolism to fluorescein monoglucuronide. After IV administration of fluorescein sodium (14 mg/kg) to 7 healthy subjects, approximately 80% of fluorescein in plasma was converted to glucuronide conjugate after a period of 1 hour post dose, indicating relatively rapid conjugation.
Fluorescein is a known human metabolite of zinc15020070.
Route of Elimination: Fluorescein and its metabolites are mainly eliminated via renal excretion.

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Biological Half-Life
... The pharmacokinetics of fluorescein and fluorescein glucuronide /were studied/ for 38 hr in the plasma of five normal subjects given 14 mg/kg of sodium fluorescein intravenously. ... The terminal half-lives of fluorescein and fluorescein glucuronide in the plasma ultrafiltrate were 23.5 and 264 min, respectively, ... .

Toxicity Summary
Fluorescein sodium is used extensively as a diagnostic tool in the field of ophthalmology. Fluorescein is a fluorescent compound or fluorophore having a maximum absorbance of 494 m and an emission maximum of 521 nm. The yellowish-green fluorescence of the compound can be used to demarcate the vascular area under observation, distinguishing it from adjacent areas. It is applied topically in the form of a drop or it can be injected intravenously to produce a fluorescein angiogram. Topical fluorescein is a useful tool in the diagnosis of corneal abrasions, corneal ulcers, herpetic corneal infections, and dry eye. Fluorescein angiography is used to diagnose and categorize macular degeneration, diabetic retinopathy, inflammatory intraocular conditions, and intraocular tumors.

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Because absorption from the eye is limited, fluorescein would not be expected to cause any adverse effects in breastfed infants. To substantially diminish the amount of drug that reaches the breastmilk after using eye drops, place pressure over the tear duct by the corner of the eye for 1 minute or more, then remove the excess solution with an absorbent tissue.
After intravenous use in a nursing mother, milk levels and the dose received by the infant are much higher than with ophthalmic use. It is unlikely that these higher levels are problematic for most infants, but exposure to intense light, such as phototherapy, should probably be avoided for a few days after the maternal dose.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
85%

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Non-Human Toxicity Values
LD50 Mouse approx 4738 mg/kg /Sodium fluorescein/
LD50 Rat approx 6721 mg/kg /Sodium fluorescein/

[1]. Fluorescein dye derivatives and their nanohybrids: Synthesis, characterization and antimicrobial activity. J Photochem Photobiol B. 2016 Sep;162:421-433.

[2]. Analysis of chemical equilibrium of silicon-substituted fluorescein and its application to develop a scaffold for red fluorescent probes. Anal Chem. 2015;87(17):9061-9069.

[3]. Fluorescein as an artificial enzyme to mimic peroxidase. Chem Commun (Camb). 2016 Nov24;52(96):13912-13915.

[4]. Absorption and fluorescence properties of fluorescein. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.

Therapeutic Uses
Contrast Medium
VET: Deep corneal ulcers, descemetocele, and iris prolapse are seen with some frequency in dogs, cats, and horses. ... Important diagnostic aids are the Schirmer tear test to measure aqueous tear production and topical fluorescein to examine the corneal ulcer. ...
Fluorescein is now sometimes used for determination of circulation time, adequacy of blood supply, and viability of tissue.
In determination of circulation time, ... by rapid iv ... appearance of fluorescence in lips, eyes, or intact skin or in wheals (histamine or scratch) ... is taken as end point.
Measurement of arm-to-retina circulation time is employed for diagnosis of carotid artery occlusion.

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Drug Warnings
Adverse effects following topical administration to the eye may include irritation and rash. Fluorescein may cause yellow discoloration of skin or eyes. urine may attain a bright yellow color. Adverse effects following intravenous administration include nausea, vomiting, headache, dizziness, fainting, and low blood pressure.

C20H12O5

332.3063

332.068

2321-07-5

Fluorescein sodium;518-47-8

16850

Pink to red solid powder

1.6±0.1 g/cm3

620.8±55.0 °C at 760 mmHg

320 °C(lit.)

232.6±25.0 °C

0.0±1.9 mmHg at 25°C

1.792

2.98

2

5

0

25

522

0

GNBHRKFJIUUOQI-UHFFFAOYSA-N

InChI=1S/C20H12O5/c21-11-5-7-15-17(9-11)24-18-10-12(22)6-8-16(18)20(15)14-4-2-1-3-13(14)19(23)25-20/h1-10,21-22H

3',6'-dihydroxyspiro[2-benzofuran-3,9'-xanthene]-1-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~250 mg/mL (~752.31 mM)
H2O : ~1 mg/mL (~3.01 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (6.26 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (6.26 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)