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: Time after dose administration (hrs) and Average plasma concentration (mcg/mL)
|Dose/route||0.5 hr||1 hr||2 hr||4 hr||6 hr||8 hr||12 hr||16 hr||24 hr|
|0.5 g IV||82||59||48||37||29||23||15||10||5|
|0.5 g IM||22||33||38||35||30||26||16||unknown||5|
Table 2: Time after dose administration (hrs) and Average urine concentration (mcg/mL)
|Dose/route||0-2 hrs||2-4 hrs||4-8 hrs||8-12 hrs||12-24 hrs||24-48 hrs|
|0.5 g IV||526||366||142||87||70||15|
|0.5 g IM||115||425||308||127||96||28|
- 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 theoretically give IV ceftriaxone for gonorrhea instead of IM .
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.
- Product Information: ROCEPHIN(R) IV, IM injection, ceftriaxone sodium IV, IM injection. Genentech USA, Inc. (per Manufacturer), South San Francisco, CA, 2010.
- 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: August 24, 2013