How many times have you given your patient IM ceftriaxone for that presumed gonococcal infection? … still counting? Many of us learned (or at least thought we learned) that ceftriaxone has to be administered IM to get the ‘depot’ effect.

Myth Busted 

There doesn’t appear to be a true depot effect. IV and IM ceftriaxone have very similar pharmacokinetic profiles. Let me prove it to you, straight from the FDA-approved ceftriaxone package insert.

Table 1: Average plasma concentration (mcg/mL) as measured over time after 500 mg of ceftriaxone administration

Ceftriaxone route0.5 hr1 hr2 hr4 hr6 hr8 hr12 hr16 hr24 hr


Table 2: Average urine concentration (mcg/mL) as measured over time after 500 mg of ceftriaxone administration

Ceftriaxone route0-2 hrs2-4 hrs4-8 hrs8-12 hrs12-24 hrs24-48 hrs
  • The plasma concentrations are almost identical after IM and IV administration through 24 hours (Table 1).
  • Even the urinary concentrations are similar up to 24-48 hours after a dose (Table 2).
  • The volume of distribution is the same for both parenteral routes, too. This means that its penetration into the “affected area” is similar.
  • According to a 2012 CDC Report the minimum inhibitory concentration (MIC) for N. gonorrhoeae strains to ceftriaxone is 0.125 mcg/mL. IV therapy provides concentrations above this resistance cutoff well after 24-48 hours, similar to IM therapy.

Trick of the Trade

If the patient already has an IV line, we can give IV ceftriaxone for gonorrhea instead of IM.

In fact, the Japanese Society for Sexually Transmitted Diseases has recommended monotherapy with a single IV dose of 1 g ceftriaxone since 2008. (Aoki 2021)

While most of the time patients with STD (or STI, if you prefer) complaints don’t have an IV line established, occasionally they do. My hospital stocks 1 gm and 2 gm premixed IV bags of ceftriaxone, so we could potentially just give 1 gm IV in these rare cases to ensure adequate levels (even 500 mg might be just fine).

Of course, the other way to avoid the painful injection is to mix the ceftriaxone with lidocaine… or avoid contracting gonorrhea altogether.


This post is intended for educational purposes to explore the kinetic data for IM and IV therapy. The CDC guidelines should be followed for treatment of STDs.


  1. Product Information: ROCEPHIN(R) IV, IM injection, ceftriaxone sodium IV, IM injection. Genentech USA, Inc. (per Manufacturer), South San Francisco, CA, 2010.
  2. Workowski KA, Berman S; Centers for Disease Control and Prevention (CDC). Sexually transmitted diseases treatment guidelines, 2010. MMWR Recomm Rep 2010;59(RR-12):1-110. [PMID: 21160459]. Free MMWR PDF download.

Original: October 9, 2012; Last Updated: December 24, 2021

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Leadership Team, ALiEM
Creator and Lead Editor, Capsules and EM Pharm Pearls Series
Attending Pharmacist, EM and Toxicology, MGH
Associate Professor of EM, Division of Medical Toxicology, Harvard Medical School
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP


EM Pharmacist & Toxicologist @MassGeneralEM | Asst Prof @HarvardMed/@EMRES_MGHBWH | @ALiEMteam leadership | Capsules creator, ALiEMU | President, ABAT | #FOAMed