Immune & Pharm Flashcards
Valacyclovir bioavailability vs acyclovir
Valacyclovir is the amino acid ester prodrug of acyclovir and has a much higher bioavailability compared to acyclovir alone (54% vs 20%). It is typically dosed at 1 gram tid for 7-14 days when used for herpes zoster (HZV) infections.
Thygeson’s
This patient presents with photophobia and foreign body sensation in the presence of a cluster of corneal epithelial lesions. These lesions would likely stain “negatively” with fluorescein. In addition, both eyes are affected and the lesions are concentrated centrally on both corneas. This is the classic presentation for Thygeson superficial punctate keratitis which first was described by Phillips Thygeson in 1950.
The etiology of Thygeson’s is currently unknown. The classic corneal findings consist of ~15-20 discrete, round/oval, punctate intraepithelial deposits that are concentrated in the central cornea. The conjunctival is mildly injected or entirely quiet. The bouts of foreign body sensation typically last ~1-2 months with a similar time period of remission.
The best initial treatment for this disorder are artificial tears especially in mild-to-moderate cases. The corneal lesions are very sensitive to steroid treatment but have a high rate of recurrence once the drops are stopped. Conservative treatment is the best first-line approach. If artificial tears and corticosteroids are not effective and/or contraindicated, then one can consider alternative treatments such as:
cyclosporin eyedrops (e.g. 0.5% or 2%)
bandage contact lenses
tacrolimus (aka FK506)
Fluoromethalone 0.1% (choice “A”) would be effective, but is not an option for this patient since she absolutely cannot use corticosteroids. Lastly, epithelial debridement (“B”) and ketorolac (“C”) have not been shown to be effective for Thygeon’s SPK.
Famciclovir - what is it a prodrug for?
prodrug of penciclovir and is also used in the treatment of acute HZV infections (typical dosage: 500 mg tid for 7 days).
Ganciclovir - how is it activated?
Ganciclovir is not a prodrug, but instead must be phosphorylated (e.g. by viral thymidine kinase) to become activated. In Ophthalmology, it is used primarily for cytomegalovirus retinitis. Although it is effective against other herpesvirus infections, its use is restricted due to its severe side effect profile (e.g. myelosuppression).
potential complications of MMC
Complications: Non-healing corneal epithelial defects, infectious sclerokeratitis
most dreaded complication being scleral melt/necrosis. Infectious sclerokeratitis occurs because the eye is placed into a reduced immune level and superinfection can occur.
Rx of gonococcal conjunctivitis
Due to the high rate of co-infection with Chlamydia, it is generally suggested that patients with gonococcal conjunctivitis also be treated for Chlamydia. The best treatment options for Chlamydia are doxycycline or azithromycin.
This question does not give an answer choice to treat both gonococcal conjunctivitis and Chlamydia so choose the best option (to treat just the gonococcal conjunctivitis in this case). Rx is with IM ceftriaxone.
Mnemonic: If you have chalmydia, you are a CAD (chlamydia = azithromycin, doycycline). G/C = gonorrhea = cefritaxone
neurotrophic ulcers and meds
Topical ß blockers, topical CAIs, topical anesthetic abuse, topical NSAIDs, topical trifluridine (Viroptic), and corneal herpes zoster can all lead to neurotrophic ulcers. In addition, drops containing the preservative Benzalconium Choloride (BAK) cause neurotrophic keratopathy.
young patient is presenting with bilateral HSV epithelial keratitis. Suspicious for?
should raise suspicion that the patient is immunocompromised (possibly with AIDs). Patients who are immunocompromised and who take valacyclovir (Valtrex) can develop thrombotic thrombocytopenic purpura and hemolytic uremia syndrome
In Mooren ulcer, which type of cells present in increased concentration
plasma cells
