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About Michelle Lin, MD

ALiEM Founder and CEO
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
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Trick of the Trade: IV ceftriaxone for gonorrhea

Clinician administering an intramuscular ceftriaxone injection into a patient's upper arm

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.

Ceftriaxone route 0.5 hr 1 hr 2 hr 4 hr 6 hr 8 hr 12 hr 16 hr 24 hr
IV 82 59 48 37 29 23 15 10 5
IM 22 33 38 35 30 26 16 unknown 5

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

Ceftriaxone route 0-2 hrs 2-4 hrs 4-8 hrs 8-12 hrs 12-24 hrs 24-48 hrs
IV 526 366 142 87 70 15
IM 115 425 308 127 96 28

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

  • 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.

Disclaimer

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.

2026 editor’s update: Current CDC guidance (the 2021 STI Treatment Guidelines, still in effect) recommends a single dose of ceftriaxone 500 mg IM (1 g IM if ≥150 kg) as monotherapy for uncomplicated gonorrhea — up from the 250 mg dose referenced in the 2010 guidelines cited below. Add doxycycline 100 mg PO twice daily for 7 days if chlamydia coinfection hasn’t been excluded. The IV/IM equivalence data below still holds — only the recommended dose has changed.

References

  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, Bachmann LH, Chan PA, et al.; Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep 2021;70(4):1-187. [PMID: 34292926]. Free CDC PDF download.

Original: October 9, 2012; Last Updated: August 10, 2026

By |2026-08-10T15:59:03-07:00Oct 9, 2012|Infectious Disease, Tox & Medications, Tricks of the Trade|
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PV Card: Electrolytes and ECG changes

ECG anatomy segments

The electrocardiogram can pick up all sorts of electrolyte abnormalities. The most common abnormalities revolve around high and low levels of potassium and calcium. Magnesium derangements typically have nonspecific findings. How do you keep things straight? To make things more complicated, multiple electrolyte derangements can occur at the same time, making ECG interpretation challenging.

(more…)

By |2021-10-08T09:38:57-07:00Sep 21, 2012|ALiEM Cards, ECG, Endocrine-Metabolic|
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