February 13, 2023
I’m the first FDA-approved antiviral drug.
What molecule am I?
Image of Idoxuridine 3D Image of Idoxuridine

Idoxuridine is an iodinated analogue of the nucleosides deoxyuridine and thymidine. It was first synthesized by William H. Prusoff at Yale University (New Haven, CT) in 1958. Five years later, it became the first antiviral drug approved by the US Food and Drug Administration, for topical use against herpes simplex keratitis.

Idoxuridine in solution or ointment form also has ophthalmic applications. It cannot be administered internally because it is cardiotoxic.

If idoxuridine is the oldest antiviral, what is the newest? One candidate is lufotrelvir1, a compound disclosed in 2020 by researchers at multiple laboratories of Pfizer Worldwide Research and Development and other institutions. Lufotrelvir is a potential treatment for COVID-19, although, unlike some others, it must be administered intravenously. This month, Robert A. Singer and co-workers at Pfizer (Groton, CT) reported an improved synthesis of the relatively unstable lufotrelvir.

1. CAS Reg. No. 2468015-78-1.

Idoxuridine hazard information*

Hazard class**GHS code and hazard statement
Acute toxicity, oral, category 4H302—Harmful if swallowedChemical Safety Warning
Acute toxicity, dermal, category 4H312—Harmful in contact with skinChemical Safety Warning
Skin corrosion/irritation, category 2H315—Causes skin irritationChemical Safety Warning
Serious eye damage/eye irritation, category 2AH319—Causes serious eye irritationChemical Safety Warning
Acute toxicity, inhalation, category 4H332—Harmful if inhaledChemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3H335—May cause respiratory irritationChemical Safety Warning
Germ cell mutagenicity, category 2H341—Suspected of causing genetic defectsChemical Safety Warning
Reproductive toxicity, category 2H361—Suspected of damaging fertility or the unborn childChemical Safety Warning

*Compilation of multiple safety data sheets.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Molecules from the journals

2,3,5-Trimethylpyrazine1 is a widely used synthetic flavor and aroma additive for foods. Described as imparting nutty, earthy, or “roasty” characteristics, it is used for enhancing coffee, chocolate products, and cereals, among others. This past November, Roman Lang and co-workers at Technical University Munich (Freising, Germany) described an analytical method for determining 2,3,5-trimethylpyrazine metabolites in human urine.

Obeticholic acid2 (6α-ethylchenodeoxycholic acid) is a first-in-class farnesoid ester X receptor agonist used to treat primary biliary cirrhosis and nonalcoholic steatohepatitis. It was developed by Intercept Pharma (Morristown, NJ) and approved by the US Food and Drug Administration in 2016 under the tradename Ocaliva. In November, Vijayavitthal T. Mathad and colleagues at MSN Laboratories (Hyderabad, India) reported an efficient synthesis of obeticholic acid that minimizes process-related and diastereomeric impurities.

Europium(III) oxide3 (Eu2O3) is widely used as a color-producing phosphor in television screens and as a fluorescent component in glassware; it is also used in paper currency for counterfeit detection. But Eu2O3 and other lanthanide oxides are also constituents of radioactive nuclear waste that must be separated from actinide oxides during waste treatment. In December, Prasanta Kumar Mohapatra and co-workers at Bhabha Atomic Research Center (Mumbai, India) identified an ionic liquid that can be used to separate Eu2O3 from americium and uranium oxides in a liquid–liquid extraction process under ambient conditions. The actinide oxides are poorly soluble in the ionic liquid.

1. CAS Reg. No. 14667-55-1.
2. CAS Reg. No. 459789-99-2.
3. CAS Reg. No. 1308-96-9.

Molecules from the Journals

MOTW briefly describes noteworthy molecules that appeared in recent ACS journal articles. See this week's
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Idoxuridine fast facts

CAS Reg. No.54-42-2
SciFinder nomenclatureUridine, 2′-deoxy-5-iodo-
Empirical formulaC9H11IN2O5
Molar mass354.10 g/mol
AppearanceWhite crystals or powder
Melting pointValues reported from 170 to 263 °C
Water solubility2 g/L
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Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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