Usage
Idoxuridine is primarily indicated for the treatment of herpes simplex keratitis, a viral infection of the cornea caused by the herpes simplex virus (HSV). It is classified as an antiviral agent.
Idoxuridine’s mechanism of action involves inhibiting viral DNA replication. As a thymidine analog, it gets incorporated into the viral DNA, disrupting further viral replication and thus halting the progression of the infection.
Alternate Names
- 5-Iodo-2’-deoxyuridine
- 5-IUdR
- IdUrd
- IDU
Brand names: Herplex, Stoxil (no longer available in the United States)
How It Works
Pharmacodynamics: Idoxuridine exerts its antiviral effect by inhibiting viral DNA synthesis and function. The incorporation of idoxuridine into viral DNA results in the production of non-functional viral particles, preventing further viral replication.
Pharmacokinetics: Idoxuridine is primarily administered topically as an ophthalmic solution or ointment. Systemic absorption is minimal with topical application. When administered systemically, the drug is rapidly metabolized and excreted primarily through the kidneys.
- It does not bind to receptors, but rather becomes incorporated into viral DNA, acting as a chain terminator for DNA polymerase.
- It inhibits the enzyme DNA polymerase to interrupt viral replication.
- Elimination occurs through renal excretion. Minimal metabolism by CYP enzymes has been reported.
Dosage
Standard Dosage
Adults:
Ophthalmic solution (0.1%): Instill one drop into the affected eye(s) every hour during the day and every two hours at night. After improvement, reduce the frequency to every two hours during the day and every four hours at night.
Ophthalmic ointment (0.5%): Apply a 1/2-inch ribbon of ointment inside the lower eyelid of the affected eye(s) five times daily, approximately every 3 hours while awake.
Children:
Similar dosing as adults. Pediatric safety has not been extensively studied.
Special Cases:
- Elderly Patients: No specific dose adjustments are typically required.
- Patients with Renal Impairment: Due to minimal systemic absorption with topical ophthalmic use, dose adjustments are typically not necessary. Systemic administration should be done cautiously. Monitor renal function.
- Patients with Hepatic Dysfunction: Caution is advised with systemic administration; monitor liver function. Topical ophthalmic use does not generally require adjustments.
- Patients with Comorbid Conditions: Exercise caution and consider individual patient factors.
Clinical Use Cases
Idoxuridine is specifically used for herpes simplex keratitis. It is not indicated for the clinical situations listed (intubation, surgical procedures, mechanical ventilation, ICU use, emergency situations).
Dosage Adjustments
Dose adjustments may be needed based on the patient’s response to therapy and ocular tolerance.
Side Effects
Common Side Effects
- Ocular irritation (burning, stinging)
- Itching
- Redness
- Swelling of the eyelids
- Photophobia
- Blurred vision
Rare but Serious Side Effects
- Corneal clouding or ulceration
- Allergic reactions
Long-Term Effects
Corneal thinning or scarring may occur with prolonged use.
Adverse Drug Reactions (ADR)
Severe allergic reactions (anaphylaxis), although rare, may occur.
Contraindications
- Hypersensitivity to idoxuridine.
Drug Interactions
- Concurrent use with topical corticosteroids should be avoided or closely monitored as it may exacerbate corneal complications.
- Boric acid-containing ophthalmic preparations can reduce idoxuridine’s effectiveness.
Pregnancy and Breastfeeding
- Idoxuridine is not recommended during pregnancy unless absolutely necessary. It may pose a risk of fetal harm based on animal data.
- Use with caution during breastfeeding due to potential excretion in breast milk.
Drug Profile Summary
- Mechanism of Action: Inhibits viral DNA synthesis and replication by acting as a thymidine analog and inhibiting DNA polymerase.
- Side Effects: Ocular irritation, itching, redness, swelling, photophobia, blurred vision. Rarely: corneal clouding or ulceration, allergic reactions.
- Contraindications: Hypersensitivity to idoxuridine.
- Drug Interactions: Corticosteroids (topical), boric acid (ophthalmic preparations).
- Pregnancy & Breastfeeding: Not recommended during pregnancy; use with caution while breastfeeding.
- Dosage: Ophthalmic solution (0.1%): 1 drop every hour (day), every 2 hours (night); after improvement, decrease frequency. Ointment (0.5%): Apply 1/2-inch ribbon 5 times/day.
- Monitoring Parameters: Visual acuity, corneal integrity.
Popular Combinations
Idoxuridine is generally used as a monotherapy. Combining it with other antivirals is not routine practice.
Precautions
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General Precautions: Perform a thorough ophthalmic examination before initiating treatment. Monitor for adverse effects.
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Specific Populations: Pregnant women: Avoid unless absolutely necessary. Breastfeeding mothers: Use with caution. Children: No significant age-related dose adjustments. Elderly: No specific precautions.
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Lifestyle Considerations: No specific lifestyle restrictions are generally necessary except protection from bright light due to potential photophobia.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Idoxuridine?
A: Adults and children: Ophthalmic solution (0.1%): Instill 1 drop every hour during the day, every 2 hours at night; reduce frequency after improvement. Ointment (0.5%): Apply a 1/2-inch ribbon five times/day.
Q2: What is the mechanism of action of Idoxuridine?
A: It inhibits viral DNA synthesis and replication by acting as a thymidine analog and inhibiting DNA polymerase.
Q3: What are the common side effects of Idoxuridine?
A: Common side effects include ocular irritation (burning, stinging), itching, redness, swelling of the eyelids, photophobia, and blurred vision.
Q4: Is Idoxuridine safe during pregnancy?
A: No. Idoxuridine is generally not recommended for use during pregnancy unless absolutely necessary due to potential fetal harm.
A: Contact lens wear should be avoided during treatment with idoxuridine unless specifically advised by an ophthalmologist.
Q6: How long should Idoxuridine treatment be continued?
A: Treatment should be continued for at least 7 days, even if symptoms improve, and for 3-4 days after healing is complete as determined by fluorescein staining and clinical evaluation.
Q7: What are the contraindications to Idoxuridine use?
A: Known hypersensitivity to idoxuridine is a contraindication to its use.
Q8: How should Idoxuridine ophthalmic preparations be stored?
A: Store at room temperature and protect from excessive heat and moisture.
Q9: What should patients do if they miss a dose of Idoxuridine?
A: Instill the missed dose as soon as remembered. If near the time of the next dose, skip the missed dose and resume the regular dosing schedule. Do not double the dose.
Q10: Are there any drug interactions I should be aware of with Idoxuridine?
A: Concurrent use with topical corticosteroids should be avoided or very closely monitored, and boric acid can reduce its effectiveness.
