We have all had a patient or two request admission for intravenous antibiotics. Usually, the argument is that IV administration is better because it ‘gets into the blood more quickly’. In fact, many of us have made that argument ourselves, or heard it from our peers.
But, what if I told you that many of your favourite antibiotics have similar pharmacokinetic properties regardless of the route of administration? What if I also showed you that patient outcomes don’t change much, regardless of whether you choose oral or intravenous administration? What if you knew that intravenous antibiotics (usually several dollars per dose) are significantly more expensive than oral (usually pennies per dose)?
Well, brace yourself, because levofloxacin , ciprofloxacin ,clindamycin , and amoxicillin  are all rapidly absorbed when taken orally; in fact, each of these antibiotics has similar pharmacokinetics across oral and intravenous routes. Additionally, though there is no evidence comparing PO to IV azithromycin, the package insert  suggests a higher concentration for the first 24 hours with use of the IV version of the drug; the clinical relevance of this fact is yet to be determined.
If an antibiotic has similar bioavailability regardless of route, the route of administration should not affect clinical outcomes. So let’s examine so evidence:
Children with Pneumonia
In one trial that included tertiary care centres in Africa, Asia, and South America , 1702 children aged 3-59 months were admitted with pneumonia, and randomized to receive either PO amoxicillin or IV penicillin for 48 hours. If they improved clinically, children in either treatment arm were discharged home with a five-day course of oral amoxicillin. Treatment failure was 19% in both arms. This study was reproduced on a small scale in England in 2010 . Two hundred thirty-two children were again randomized to PO amoxicillin or IV penicillin. Similar results were obtained, with the additional finding that children receiving IV antibiotics had longer stays in hospital (3.12 vs 1.93 days) and IV treatment was more expensive (£1256 vs £769).
Adults with Lower Respiratory Tract Infection
In one study in Dublin, Ireland , 541 adult patients were admitted for lower respiratory tract infection were randomized to one of three conditions: PO amoxicillin-clavulinic acid; IV amoxicillin-clavulinic acid transitioning to PO; or an IV cephalosporin transitioning to a PO cephalosporin. The researchers found no significant differences in clinical outcome or mortality among the three groups. Lengths of stay were 6, 7, and 9 days respectively.
Adults & Children with Severe Urinary Tract Infections
A Cochrane Review in 2008  was unable to find evidence to support the superiority of IV antibiotic treatment over oral both adults or children.
Dare we Choose More Wisely?
Early conversion to PO antibiotics on the wards can lead to significant cost savings. The evidence reviewed here suggests that these savings do not come at the expense of safety. The CDC has gathered a nice collection of papers here . The most recently cited study suggests $4,404 savings from decreased utilization of radiology, laboratory, pharmacy, and room costs. Costs in the United States can vary widely among hospitals, but the message is clear: Oral antibiotics save money without comprising effectiveness.
Next time you prescribe antibiotics in the emergency department, start the patient off right. Provide an oral dose of an appropriate antibiotic, whenever possible. You will set the course for a shorter, less expensive hospital stay for your patient without compromising his or her safety. Reigning in costs for both the system and patient as well as providing evidence-based care is at the crux of the Choosing Wisely Campaign.
- Fish, D. N., & Chow, A. T. (1997). The clinical pharmacokinetics of levofloxacin.Clinical pharmacokinetics, 32(2), 101-119.
- Lettieri, J. T., Rogge, M. C., Kaiser, L., Echols, R. M., & Heller, A. H. (1992). Pharmacokinetic profiles of ciprofloxacin after single intravenous and oral doses. Antimicrobial agents and chemotherapy, 36(5), 993-996.
- Bouazza, N., Pestre, V., Jullien, V., Curis, E., Urien, S., Salmon, D., & Tréluyer, J. M. (2012). Population pharmacokinetics of clindamycin orally and intravenously administered in patients with osteomyelitis. British journal of clinical pharmacology, 74(6), 971-977.
- Spyker, D. A., Rugloski, R. J., Vann, R. L., & O’Brien, W. M. (1977). Pharmacokinetics of amoxicillin: dose dependence after intravenous, oral, and intramuscular administration. Antimicrobial agents and chemotherapy, 11(1), 132-141.
- Addo-Yobo, E., Chisaka, N., Hassan, M., Hibberd, P., Lozano, J. M., Jeena, P., … & Thea, D. M. (2004). Oral amoxicillin versus injectable penicillin for severe pneumonia in children aged 3 to 59 months: a randomised multicentre equivalency study. The Lancet, 364(9440), 1141-1148.
- Lorgelly, P. K., Atkinson, M., Lakhanpaul, M., Smyth, A. R., Vyas, H., Weston, V., & Stephenson, T. (2010). Oral versus iv antibiotics for community-acquired pneumonia in children: a cost-minimisation analysis. European Respiratory Journal, 35(4), 858-864.
- Chan, R., Hemeryck, L., O’Regan, M., Clancy, L., & Feely, J. (1995). Oral versus intravenous antibiotics for community acquired lower respiratory tract infection in a general hospital: open, randomised controlled trial. BMJ,310(6991), 1360-1362.
- Pohl, A. (2008). No evidence that oral antibiotic therapy is less effective for treating urinary tract infection than intravenous antibiotics. Cochrane Summaries, available at: http://summaries.cochrane.org/CD003237/no-evidence-that-oral-antibiotic-therapy-is-less-effective-for-treating-urinary-tract-infection-than-intravenous-antibiotics