# Amdinocillin pivoxil
**Amdinocillin pivoxil**, marketed as pivmecillinam and sold under the brand names Pivya (United States) and Selexid, is the pivaloyloxymethyl ester prodrug of mecillinam ([amdinocillin](https://www.edgepedia.org/amdinocillin)), an amidinopenicillin (penicillin subclass with an amidino group, here mecillinam) antibiotic taken orally to treat uncomplicated urinary tract infections.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6628187/) After oral absorption, esterases in the blood, gastrointestinal mucosa, and other tissues hydrolyze the ester to release mecillinam, the active antibacterial agent.[2](https://www.medicines.org.uk/emc/product/4982/smpc)
| Key fact | Detail |
|---|---|
| Drug class | Oral prodrug of mecillinam, an amidinopenicillin; a penicillin-class antibacterial[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6628187/) • [3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf) |
| Mechanism | Mecillinam binds selectively to penicillin-binding protein-2, a target distinct from other β-lactams[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6628187/) |
| US approval | April 2024, as Pivya, for uncomplicated UTI in women 18 and older caused by *E. coli*, *P. mirabilis*, and *S. saprophyticus*[4](https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-uncomplicated-urinary-tract-infections) |
| US dose | 185 mg orally three times daily for 3 to 7 days[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf) |
| Efficacy | Composite response rates of 62% to 72% across three pivotal trials; superior to placebo and ibuprofen, similar to cephalexin[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/) |
| Common side effects | Nausea and diarrhea[6](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=440a5f17-ab11-0fc8-e063-6394a90a58e9) |
| Key contraindications | Serious β-lactam hypersensitivity, inherited carnitine deficiency disorders, acute porphyria[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf) |
## Pharmacology
Mecillinam differs from other β-lactam antibiotics in its target: it binds with high specificity to penicillin-binding protein-2, which is probably responsible for the synergy observed with penicillins and cephalosporins.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6628187/) • [2](https://www.medicines.org.uk/emc/product/4982/smpc) The drug is active against most [Enterobacteriaceae](https://www.edgepedia.org/enterobacteriaceae), including *E. coli*, *Klebsiella*, *Proteus*, *Enterobacter*, *Serratia*, *Salmonella*, *Shigella*, and *Yersinia*, while *Pseudomonas aeruginosa* and *Streptococcus faecalis* are practically resistant.[2](https://www.medicines.org.uk/emc/product/4982/smpc)
After a 400 mg oral dose in adults, peak serum levels of mecillinam average 5 micrograms per milliliter after about 1 hour; the serum half-life is 1.2 hours, protein binding is 5 to 10 percent, and roughly half the dose is excreted as mecillinam in the urine within six hours.[2](https://www.medicines.org.uk/emc/product/4982/smpc) This urinary concentration is what confines its practical use to infections of the lower urinary tract.
## Clinical use
**Uncomplicated cystitis.** Pivmecillinam has been used for uncomplicated urinary tract infection in Europe and Canada for decades; it was first approved in Europe more than 40 years before its 2024 US approval.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/) It is the only oral β-lactam recommended as a first-line agent for uncomplicated UTI in guidelines from the Infectious Diseases Society of America, the European Society of Clinical Microbiology and Infectious Diseases, and the [European Association of Urology](https://www.edgepedia.org/european-association-of-urology).[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/) *E. coli* susceptibility rates to mecillinam typically exceed 90 percent, and mecillinam retains activity against many ESBL-producing Enterobacterales.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/)
The 2024 US approval rested on a subject-level reanalysis of three randomized controlled trials conducted under 2019 FDA criteria, in which patients received 185 mg three times daily for 3 to 7 days.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/) Overall success rates at test of cure were 62.0 to 71.7 percent, higher than placebo (95% CI for the difference, 41.2 to 62.0) and ibuprofen (31.2 to 56.5), and similar to cephalexin (−15.6 to 7.4).[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/) In the placebo-controlled trial, 62 percent of 137 patients receiving pivmecillinam achieved the composite response compared with 10 percent of 134 on placebo.[4](https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-uncomplicated-urinary-tract-infections)
**Dosing and duration.** A systematic review and meta-analysis of randomized trials concluded there is insufficient evidence to identify an optimal combination of dose, frequency, and duration of pivmecillinam for uncomplicated lower UTI.[7](https://pubmed.ncbi.nlm.nih.gov/28341436/) A randomized trial comparing 400 mg three times daily for 5 days versus 3 days found no superiority of the longer course for clinical or bacteriological outcomes, and 3 days of pivmecillinam appears comparable to 5 days of nitrofurantoin.[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC6677655/) In the SCOUT trial in Spanish primary care, clinical resolution at day 7 was 70 percent with pivmecillinam 400 mg three times daily for 3 days, versus 74 percent with nitrofurantoin and 59 percent with single-dose fosfomycin.[9](https://pubmed.ncbi.nlm.nih.gov/42026010/)
**Resistant organisms.** The British Society for Antimicrobial Chemotherapy working party found that failure rates with 200 mg three times daily against lower UTI caused by ESBL-producing *E. coli* are too high to recommend regular use, that urinary levels at that dose inadequately inhibit some CTX-M-15 producers, and that trial data are inadequate for *Klebsiella* infections.[10](https://academic.oup.com/jac/article/73/suppl_3/iii2/4915406) Against carbapenem-resistant Enterobacterales, mecillinam susceptibility was 0 percent among 174 KPC producers but 71 percent among 1,094 NDM-producing and 84 percent among 4,042 OXA-48-producing isolates, and the IDSA guidance suggests pivmecillinam as an alternative for CRE uUTI when KPC production is unlikely.[11](https://www.idsociety.org/practice-guideline/amr-guidance?n=%40)
## Safety
The most common adverse reactions in clinical trials, occurring in at least 2 percent of patients, are nausea and diarrhea.[6](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=440a5f17-ab11-0fc8-e063-6394a90a58e9) In the placebo-controlled US trial, nausea occurred in 4.3 percent and diarrhea in 2.1 percent of patients receiving pivmecillinam.[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf)
Because the prodrug releases pivalate, long-term treatment can deplete carnitine through formation and urinary excretion of pivaloylcarnitine; clinically significant hypocarnitinemia has been observed with prolonged use, and the drug is not recommended when prolonged antibacterial treatment is necessary.[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf) Pivmecillinam is contraindicated in patients with serious hypersensitivity to β-lactams, primary or secondary carnitine deficiency from inherited metabolic disorders, and acute porphyria.[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf) Treatment shortly before delivery can cause a false-positive newborn screening result for isovaleric acidemia.[3](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf)
## References
1. [Pivmecillinam for Uncomplicated Lower Urinary Tract Infections Caused by Staphylococcus saprophyticus, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC6628187/)
2. [Pivmecillinam 200mg film-coated tablets SmPC, emc](https://www.medicines.org.uk/emc/product/4982/smpc)
3. [PIVYA (pivmecillinam) prescribing information, FDA label](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/216483s000lbl.pdf)
4. [FDA Approves New Treatment for Uncomplicated Urinary Tract Infections, April 24, 2024](https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-uncomplicated-urinary-tract-infections)
5. [Pivmecillinam for Treatment of Uncomplicated Urinary Tract Infection: New Efficacy Analysis, Clinical Infectious Diseases](https://pmc.ncbi.nlm.nih.gov/articles/PMC12728296/)
6. [DailyMed – PIVYA pivmecillinam tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=440a5f17-ab11-0fc8-e063-6394a90a58e9)
7. [Optimal dosage and duration of pivmecillinam treatment for uncomplicated lower urinary tract infections: systematic review and meta-analysis](https://pubmed.ncbi.nlm.nih.gov/28341436/)
8. [Three versus five days of pivmecillinam for community-acquired uncomplicated lower urinary tract infection, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC6677655/)
9. [Clinical and bacteriological effectiveness of three different short-course antibiotic regimens and single-dose fosfomycin (SCOUT)](https://pubmed.ncbi.nlm.nih.gov/42026010/)
10. [BSAC/HIS/BIA Joint Working Party: Treatment of infections caused by multidrug-resistant Gram-negative bacteria, Journal of Antimicrobial Chemotherapy](https://academic.oup.com/jac/article/73/suppl_3/iii2/4915406)
11. [IDSA Guidance on the Treatment of Antimicrobial Resistant Gram-Negative Infections](https://www.idsociety.org/practice-guideline/amr-guidance?n=%40)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Medicines and therapeutics › Anti-infective drugs and resistance › Antibacterial drugs › Penicillins*
*Initially written Oct 20, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license