NAPLEX Question of the Week: STIs

Dosing is the focus regarding our question of the week with sexually transmitted infections.
NAPLEX Question of the Week: STIs

A 22 year old female presents with complaints of pelvic pain and increased vaginal discharge. She states that she recently had unprotected sex with a new partner. She reports no known health conditions. Which of the following correctly matches appropriate initial treatment for each sexually transmitted infection if diagnosed?

A. Gonorrhea – ceftriaxone 250 mg IV as a single dose plus azithromycin 1 g PO as a single dose

B. Chlamydia – azithromycin 500 mg PO on day 1, then 250 mg daily for 4 days

C. Primary syphilis – benzathine penicillin G 2.4 million units IM in a single dose

D. Genital herpes – acyclovir 200 mg PO daily



Answer with rationale:

The correct answer is C.

Sexually transmitted infections are extremely prevalent and patients at risk should be screened regularly. The Centers for Diseases Prevention Center (CDC) offer guideline recommendations for diagnosis, treatment, and special considerations (pregnancy, drug allergies, etc.).

Answer A is incorrect. Patients infected with Neisseria gonorrhoeae may present asymptomatic or symptomatic. Initial treatment is essential as complications may lead to disseminated gonococcal infection (i.e. septic arthritis). Due to increased resistance to the 3rd generation cephalosporin cefixime, dual therapy is now the standard of treatment. The CDC recommends gonorrhea be treated with ceftriaxone 250 mg IM as a single dose plus azithromycin 1 g PO as a single dose. In addition, dual therapy with a macrolide or doxycycline ensures Chlamydia trachomatis is covered as co-infection is very common (around 40%). While azithromycin is preferred over doxycycline due to enhanced adherance, doxycycline 100 mg orally twice daily for 7 days may be used as an alternative to azithromycin in the case of a macrolide allergy.

Answer B is incorrect. Chlamydia trachomatis is highly prevalent especially in those age ≤ 24. While many infected may be asymptomatic, screening is important as more serious complications in women may manifest as pelvic inflammatory disease (PID), ectopic pregnancy, and infertility. The CDC recommends treatment with azithromycin 1 g orally as a single dose or doxycycline 100 mg orally twice daily for 7 days. While both are equally effective, a single dose of azithromycin may offer an advantage in regards to adherence. Additionally, doxycycline is contraindicated in the second and third trimesters of pregnancy. In the case that a patient is pregnant with a macrolide allergy, amoxicillin 500 mg orally three times daily for 7 days may be used as an alternative option.

Answer C is correct. Syphilis is caused by a spirochete named Treponema pallidum and can be staged as primary and secondary, latent, and tertiary. Penicillin G is the drug of choice for all stages of syphilis. For primary and secondary syphilis, benzathine penicillin G 2.4 million units IM in a single dose is recommended. For patients who report a penicillin allergy, a thorough evaluation should be performed to assess if he/she has a true allergy. If a true penicillin allergy is present, desensitization may be performed, especially for pregnant patients or those with neurosyphilis. Additionally, if a moderate-severe IgE-mediated allergy is discerned, penicillin skin testing may be performed, if resources available, in order to remove or "de-label" the patient's medical record.

Answer D is incorrect. Genital herpes is a chronic viral infection that is caused by herpes simplex virus (HSV-1 and HSV-2). All patients who present with initial episode of genital herpes should be treated with antivirals. Treatment options for the first clinical episode of genital herpes include  acyclovir 400 mg orally three times daily, acyclovir 200 mg orally five times daily, or valacyclovir 1 g orally twice daily. Duration of treatment is usually 7-10 days but can be extended if healing is incomplete after 10 days of therapy. Suppressive therapy with these same agents at different doses/frequencies can be used to reduce frequency of recurrence.

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