Summary: A semisynthetic cephalosporin antibiotic with antimicrobial activity similar to that of CEPHALORIDINE or CEPHALOTHIN, but somewhat less potent. It is effective against both gram-positive and gram-negative organisms.

Top Publications

  1. Free A, Roth E, Dalessandro M, Hiram J, Scangarella N, Shawar R, et al. Retapamulin ointment twice daily for 5 days vs oral cephalexin twice daily for 10 days for empiric treatment of secondarily infected traumatic lesions of the skin. Skinmed. 2006;5:224-32 pubmed
    ..twice daily was evaluated in 2 identical, randomized, double-blind, double-dummy, multicenter studies vs oral cephalexin, 500 mg twice daily for 10 days, in 1904 patients with secondarily infected traumatic lesions...
  2. Saravanan M, Sri Nataraj K, Ganesh K. Hydroxypropyl methylcellulose based cephalexin extended release tablets: influence of tablet formulation, hardness and storage on in vitro release kinetics. Chem Pharm Bull (Tokyo). 2003;51:978-83 pubmed
    The object of this study was to develop hydroxypropyl methylcellulose (HPMC) based cephalexin extended release tablet, which can release the drug for six hours in predetermined rate...
  3. Nowakowski J, McKenna D, Nadelman R, Cooper D, Bittker S, Holmgren D, et al. Failure of treatment with cephalexin for Lyme disease. Arch Fam Med. 2000;9:563-7 pubmed
    ..The first-generation cephalosporin, cephalexin monohydrate, is effective for treating bacterial cellulitis but has not been recommended or studied for treating ..
  4. Rist T, Parish L, Capin L, Sulica V, Bushnell W, Cupo M. A comparison of the efficacy and safety of mupirocin cream and cephalexin in the treatment of secondarily infected eczema. Clin Exp Dermatol. 2002;27:14-20 pubmed
    The efficacy and safety of mupirocin calcium cream were compared with those of oral cephalexin in the treatment of secondarily infected eczema...
  5. Shahverdi A, Fakhimi A, Zarrini G, Dehghan G, Iranshahi M. Galbanic acid from Ferula szowitsiana enhanced the antibacterial activity of penicillin G and cephalexin against Staphylococcus aureus. Biol Pharm Bull. 2007;30:1805-7 pubmed
    ..effect of Ferula szowitsiana roots' acetone extract on the antibacterial activity of penicillin G and cephalexin was evaluated against Staphylococcus aureus...
  6. Cheng T, Chen M, Zheng H, Wang J, Yang S, Jiang W. Expression and purification of penicillin G acylase enzymes from four different micro-organisms, and a comparative evaluation of their synthesis/hydrolysis ratios for cephalexin. Protein Expr Purif. 2006;46:107-13 pubmed
    ..in a single step by agar-based Co-IDA chromatography, and were then evaluated as catalysts for the synthesis of cephalexin by a kinetically controlled strategy. We find here that the penicillin G acylase enzyme from K...
  7. Khawcharoenporn T, Tice A. Empiric outpatient therapy with trimethoprim-sulfamethoxazole, cephalexin, or clindamycin for cellulitis. Am J Med. 2010;123:942-50 pubmed publisher
    ..Limited data exist on optimal empiric oral antibiotic treatment for outpatients with cellulitis in areas with a high prevalence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections...
  8. Damborg P, Gaustad I, Olsen J, Guardabassi L. Selection of CMY-2 producing Escherichia coli in the faecal flora of dogs treated with cephalexin. Vet Microbiol. 2011;151:404-8 pubmed publisher
    b>Cephalexin is a first generation cephalosporin commonly used in dogs for treatment of pyoderma...
  9. Parish L, Jorizzo J, Breton J, Hirman J, Scangarella N, Shawar R, et al. Topical retapamulin ointment (1%, wt/wt) twice daily for 5 days versus oral cephalexin twice daily for 10 days in the treatment of secondarily infected dermatitis: results of a randomized controlled trial. J Am Acad Dermatol. 2006;55:1003-13 pubmed
    ..We sought to determine the clinical safety and efficacy of topical retapamulin ointment 1% versus oral cephalexin for the treatment of SID...

More Information


  1. Fenner J, Wiss K, Levin N. Oral cephalexin for acne vulgaris: clinical experience with 93 patients. Pediatr Dermatol. 2008;25:179-83 pubmed publisher
    For patients who fail traditional acne therapy or experience side effects, other treatments are needed. Cephalexin has been noted to be efficacious in some instances...
  2. Toma S, Colombo S, Cornegliani L, Persico P, Galzerano M, Gianino M, et al. Efficacy and tolerability of once-daily cephalexin in canine superficial pyoderma: an open controlled study. J Small Anim Pract. 2008;49:384-91 pubmed publisher
    The aims of this study were to evaluate the efficacy and tolerability of oral cephalexin given at 30 mg/kg once daily in dogs with superficial pyoderma and to compare them with those of oral cephalexin given at 15 mg/kg twice daily...
  3. Chen A, Carroll K, Diener West M, Ross T, Ordun J, Goldstein M, et al. Randomized controlled trial of cephalexin versus clindamycin for uncomplicated pediatric skin infections. Pediatrics. 2011;127:e573-80 pubmed publisher
    To compare clindamycin and cephalexin for treatment of uncomplicated skin and soft tissue infections (SSTIs) caused predominantly by community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA)...
  4. Bisaccia E, Scarborough D. Herpes simplex virus prophylaxis with famciclovir in patients undergoing aesthetic facial CO2 laser resurfacing. Cutis. 2003;72:327-8 pubmed
    ..In this small study, famciclovir 250 mg given BID for 14 days was an effective prophylactic treatment in facial laser resurfacing patients for the prevention of facial HSV reactivation. ..
  5. Hesaraki S, Nemati R. Cephalexin-loaded injectable macroporous calcium phosphate bone cement. J Biomed Mater Res B Appl Biomater. 2009;89:342-52 pubmed publisher
    ..In this study, liberation of cephalexin monohydrate (CMH) from a macroporous CPC was investigated over 0...
  6. Irvine F, McNab A. Orbital abscess following uncomplicated phacoemulsification cataract surgery. Clin Exp Ophthalmol. 2002;30:430-1 pubmed
    ..Alternatively, secondary haemorrhage with secondary infection may have occurred. ..
  7. Tanaka N, Takizawa T, Miyamoto N, Funayama S, Tanaka R, Okano S, et al. Real world data of a veterinary teaching hospital in Japan: a pilot survey of prescribed medicines. Vet Rec Open. 2017;4:e000218 pubmed publisher
    ..36 oral antipathogenic products were prescribed, and among them amoxicillin was prescribed the most, followed by cephalexin for human beings and enrofloxacin for veterinary...
  8. Vangipuram R, Hinojosa T, Lewis D, Downing C, Hixson C, Salas Alanis J, et al. Bullosis Diabeticorum: A Neglected Bullous Dermatosis. Skinmed. 2018;16:77-79 pubmed
    ..of painless, fluid-filled blisters, for which his primary care physician had treated him with doxycycline, cephalexin, and topical corticosteroids, with no significant improvement...
  9. Sui Q, Wang B, Zhao W, Huang J, Yu G, Deng S, et al. Identification of priority pharmaceuticals in the water environment of China. Chemosphere. 2012;89:280-6 pubmed publisher
  10. Chandler H, Gemensky Metzler A, Bras I, Robbin Webb T, Saville W, Colitz C. In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs. J Am Vet Med Assoc. 2010;237:378-86 pubmed publisher
    ..ophthalmic ointment containing neomycin, polymyxin B, and bacitracin (ie, triple antibiotic ointment; q 8 h); cephalexin (22 mg/kg [10 mg/lb], PO, q 12 h) with topically applied oxytetracycline ophthalmic ointment (q 8 h); or a ..
  11. Funabashi M, Funa N, Horinouchi S. Phenolic lipids synthesized by type III polyketide synthase confer penicillin resistance on Streptomyces griseus. J Biol Chem. 2008;283:13983-91 pubmed publisher
    ..which produced no phenolic lipids, was highly sensitive to beta-lactam antibiotics, such as penicillin G and cephalexin. Together with the fact that the alkylresorcinols were fractionated mainly in the cell wall fraction, this ..
  12. Maiza A, Daley Yates P. Variability in the renal clearance of cephalexin in experimental renal failure. J Pharmacokinet Biopharm. 1993;21:19-30 pubmed
    ..In this report the renal clearance of cephalexin (CLCEX) is investigated, a drug that has a different mode of renal elimination, since it is filtered, secreted, ..
  13. Takahashi T, Kaku T, Sato T, Watanabe K, Sato J. Effects of Acanthopanax senticosus HARMS extract on drug transport in human intestinal cell line Caco-2. J Nat Med. 2010;64:55-62 pubmed publisher
    ..In contrast, the A-to-B transport of cephalexin, a peptide transporter substrate, was significantly decreased by the addition of AS extract in the same manner...
  14. Hatanaka T, Kamon T, Morigaki S, Katayama K, Koizumi T. Ion pair skin transport of a zwitterionic drug, cephalexin. J Control Release. 2000;66:63-71 pubmed
    The ion pair skin transport of cephalexin was investigated using various counter ions and solvents. The permeability of cephalexin was enhanced by 1-alkylsulfonates (ASs) at pH 3.0 and by tetraalkylammoniums (AAs) at pH 7...
  15. Haruta S, Iwasaki N, Ogawara K, Higaki K, Kimura T. Absorption behavior of orally administered drugs in rats treated with propantheline. J Pharm Sci. 1998;87:1081-5 pubmed
    ..as a highly absorbable drug without the first-pass elimination, ampicillin as a poorly absorbable one, and cephalexin as a highly absorbable one via carrier-mediated transport system...
  16. Hoppe J, Schlagenhauf M. [Comparison of cefsulodin and cephalexin as selective agents in agar for Bordetella pertussis]. Immun Infekt. 1990;18:40-1 pubmed
    Cefsulodin (12 mg/l) was evaluated as an alternative to cephalexin (40 mg/l) as selective agent in agar for isolation of Bordetella pertussis from clinical specimens...
  17. Windfuhr J, Toepfner N, Steffen G, Waldfahrer F, Berner R. Clinical practice guideline: tonsillitis I. Diagnostics and nonsurgical management. Eur Arch Otorhinolaryngol. 2016;273:973-87 pubmed publisher
    ..In cases of allergy or incompatibility of penicillin, cephalosporins or macrolides (e.g. Erythromycin-estolate) are valuable alternatives. ..
  18. Cheng L, Yang C, Li H, Li M, Bai A, Ouyang Y, et al. Probing the interaction of cephalosporin with bovine serum albumin: A structural and comparative perspective. Luminescence. 2017;: pubmed publisher
    ..chose two typical antibiotics cefalexin/cefixime based on their structure, and investigated the interaction of cephalexin/cefixime with bovine serum albumin (BSA) using UV-vis absorption spectra, fluorescence spectroscopy, circular ..
  19. Zhang S, Piepers S, Shan R, Cai L, Mao S, Zou J, et al. Phenotypic and genotypic characterization of antimicrobial resistance profiles in Streptococcus dysgalactiae isolated from bovine clinical mastitis in 5 provinces of China. J Dairy Sci. 2018;101:3344-3355 pubmed publisher
    ..against those antimicrobial substances. Strikingly, 30 (34.1%) and 12 (13.6%) isolates were found resistant to cephalexin and ceftriaxone, respectively. BlaTEM, ermB, and tetM were the most prevalent resistance genes...
  20. Villa R, Belloli C, Cagnardi P, Sonzogni O, Bacchetta S, Carli S. Pharmacokinetics of cephalexin in the horse after intravenous and intramuscular administration of two formulations. Vet J. 2002;164:74-6 pubmed
  21. Prados A, Ambros L, Montoya L, Rebuelto M. Chronopharmacological study of cephalexin in dogs. Chronobiol Int. 2007;24:161-70 pubmed
    ..of this study was to assess the hypothesis that the absorption of the first-generation cephalosporin antibiotic cephalexin by dogs would be less and the elimination would be slower after evening (rest span) compared to morning (..
  22. Grunwald M, Shai A, Mosovich B, Avinoach I. Tungiasis. Australas J Dermatol. 2000;41:46-7 pubmed
    ..The diagnosis of tungiasis was established by microscopic examination of a lesion. Tungiasis is rarely seen in non-endemic areas. ..
  23. Huan Y, Feng G, Wang B, Ren Y, Fei Q. Quantitative analysis of cefalexin based on artificial neural networks combined with modified genetic algorithm using short near-infrared spectroscopy. Spectrochim Acta A Mol Biomol Spectrosc. 2013;109:308-12 pubmed publisher
    ..In order to enhancing the predictive ability of artificial neural networks model, a modified genetic algorithm was used to select fixed number of wavelength. ..
  24. Ambros L, Kreil V, Tarragona L, Monfrinotti A, Hallu R, Rebuelto M. Comparative pharmacokinetics of intravenous cephalexin in pregnant, lactating, and nonpregnant, nonlactating goats. J Vet Pharmacol Ther. 2011;34:397-402 pubmed publisher
    The aims of this study were to describe and compare the pharmacokinetics of a single dose of cephalexin (10 mg/kg) after its intravenous (i.v...
  25. Gouin S, Chevalier I, Gauthier M, Lamarre V. Prospective evaluation of the management of moderate to severe cellulitis with parenteral antibiotics at a paediatric day treatment centre. J Paediatr Child Health. 2008;44:214-8 pubmed
    ..8%. Treatment with parenteral antibiotic at a DTC is a viable alternative to hospitalisation for moderate to severe cellulitis in children. ..
  26. Chien A, Qi J, Rainer B, Sachs D, Helfrich Y. Treatment of Acne in Pregnancy. J Am Board Fam Med. 2016;29:254-62 pubmed publisher
    ..Oral erythromycin or cephalexin is generally considered safe for moderate to severe inflammatory acne when used for a few weeks...
  27. Lańcut M, Zarebska A, Sekita Krzak J, Czerny K. Histological changes of white rat kidney after experimental administration of ethanol and cephalexin. Ann Univ Mariae Curie Sklodowska Med. 2003;58:268-72 pubmed
    ..Animals from experimental group I received cephalexin in the single dose of 42 mg/24h, Animals from experimental group II received cephalexin in the dose of 42 mg/24h ..
  28. Chung H, Yao Z, Goehring N, Kishony R, Beckwith J, Kahne D. Rapid beta-lactam-induced lysis requires successful assembly of the cell division machinery. Proc Natl Acad Sci U S A. 2009;106:21872-7 pubmed publisher
    ..These filaments ultimately lyse through a poorly understood mechanism. Here we find that one such beta-lactam, cephalexin, can, under certain conditions, lead instead to rapid lysis at nascent division sites through a process that ..
  29. do Nascimento T, de Jesus Oliveira E, Basílio Júnior I, de Araújo Júnior J, Macedo R. Short-term stability studies of ampicillin and cephalexin in aqueous solution and human plasma: Application of least squares method in Arrhenius equation. J Pharm Biomed Anal. 2013;73:59-64 pubmed publisher
    ..This paper describes stability studies of ampicillin and cephalexin in aqueous solution and human plasma applying the Arrhenius law for determination of adequate temperature and ..
  30. Dudley M, Blaser J, Gilbert D, Zinner S. Significance of "extravascular" protein binding for antimicrobial pharmacodynamics in an in vitro capillary model of infection. Antimicrob Agents Chemother. 1990;34:98-101 pubmed
    ..Simulated 500-mg oral doses of dicloxacillin (approximately 96% bound) or cephalexin (less than 5% bound) were administered every 6 h for four doses...
  31. Cuschieri L, Debosz J, Miiller P, Celis M. Autolytic debridement of a large, necrotic, fully occluded foot ulcer using a hydrocolloid dressing in a diabetic patient. Adv Skin Wound Care. 2013;26:300-4 pubmed publisher
    ..Frequent monitoring and dressing change are also mandatory. ..
  32. Zhao R, Shu M, Chen S. [Impact of non-target gene mutations and reduced permeability of outer membrane on quinolone resistance and multiple antibiotic resistance in Escherichia coli]. Hunan Yi Ke Da Xue Xue Bao. 2003;28:263-5 pubmed
  33. Ferreira A, Bolland M, Thomas M. Meta-analysis of randomised trials comparing a penicillin or cephalosporin with a macrolide or lincosamide in the treatment of cellulitis or erysipelas. Infection. 2016;44:607-15 pubmed publisher
    Beta-lactam antibiotics, such as penicillin, flucloxacillin or cephalexin, are widely considered first-line treatment for cellulitis and erysipelas, while macrolides and lincosamides, such as erythromycin, azithromycin or clindamycin, are ..
  34. Kitaura T, Tsukiai S, Arai S, Miyake K, Kimura M, Fukuchi H. Ocular pharmacokinetics of latamoxef and cefaclor in humans. Penetration into aqueous humor. J Pharmacobiodyn. 1989;12:60-6 pubmed
    ..The predicted concentration in aqueous humor was proved to fit reasonably with the measured concentration. ..
  35. Serna Galvis E, Ferraro F, Silva Agredo J, Torres Palma R. Degradation of highly consumed fluoroquinolones, penicillins and cephalosporins in distilled water and simulated hospital wastewater by UV254 and UV254/persulfate processes. Water Res. 2017;122:128-138 pubmed publisher
    In this work, three penicillins (ampicillin "AMP", oxacillin "OXA" and cloxacillin "CLO"), two cephalosporins (cephalexin "CPX" and cephadroxyl "CPD") and three fluoroquinolones (levofloxacin "LEV", norfloxacin "NOR" and ciprofloxacin "..
  36. Kumar K, Srinivasan V, Toles R, Miner V, Jackson W, Seed T. High-dose antibiotic therapy is superior to a 3-drug combination of prostanoids and lipid A derivative in protecting irradiated canines. J Radiat Res. 2002;43:361-70 pubmed
    ..also given clinical support, which consisted of blood transfusion and antibiotics (gentamicin, and cefoxitin or cephalexin). Peripheral blood cell profile and 60-day survival were used as indices of protection. At 3...
  37. Shao D, Yao L, Riaz M, Zhu J, Shi J, Jin M, et al. Simulated microgravity affects some biological characteristics of Lactobacillus acidophilus. Appl Microbiol Biotechnol. 2017;101:3439-3449 pubmed publisher
    ..acidophilus related to human health. These findings provided valuable information for understanding the influence of probiotics on human health under simulated microgravity conditions, at least. ..
  38. Newell A, Bunting P, Anson K, Fox E. Multicentre audit of the treatment of uncomplicated urinary tract infection in South Thames. Int J STD AIDS. 2005;16:74-7 pubmed
    ..The incidence of trimethoprim resistance was 22.6%. The group has therefore recommended that cephalexin should be the first choice antibiotic for suspected UTIs within GU medicine.
  39. Liu R, Tang A, Tan Y, Limenta L, Lee E. Interethnic differences of PEPT2 (SLC15A2) polymorphism distribution and associations with cephalexin pharmacokinetics in healthy Asian subjects. Eur J Clin Pharmacol. 2009;65:65-70 pubmed publisher
    ..Asian Indian), PEPT2 haplotype and cephalexin pharmacokinetics in healthy Asian subjects...
  40. Shiau C, Pai S, Lin W, Ji D, Liu Y. Purification and characterization of inducible cephalexin synthesizing enzyme in Gluconobacter oxydans. Biosci Biotechnol Biochem. 2005;69:463-9 pubmed
    b>Cephalexin synthesizing enzyme (CSE) of Gluconobacter oxydans ATCC 9324 was purified up to about 940-fold at a yield of 12%. CSE biosynthesis in G...
  41. Zarebska A, Bakiera K, Visconti J, Kwietniewska M, Czerny K. Histological changes in the pancreas of white rats after administering cephalexin and ethanol. Ann Univ Mariae Curie Sklodowska Med. 2002;57:167-73 pubmed
    ..of experimental group I were administered 20% ethyl alcohol for drinking, animals of experimental group II--cephalexin in the dose of 42 mg daily, animals of experimental group III--simultaneously alcohol and cephalexin in the ..
  42. Moran G, Krishnadasan A, Mower W, Abrahamian F, LoVecchio F, Steele M, et al. Effect of Cephalexin Plus Trimethoprim-Sulfamethoxazole vs Cephalexin Alone on Clinical Cure of Uncomplicated Cellulitis: A Randomized Clinical Trial. JAMA. 2017;317:2088-2096 pubmed publisher
    ..It is unknown if antimicrobial regimens possessing in vitro MRSA activity provide improved outcomes compared with treatments lacking MRSA activity...
  43. Jalali H, Salamatzadeh A, Jalali A, Kashani H, Asbchin S, Issazadeh K. Antagonistic Activity of Nocardia brasiliensis PTCC 1422 Against Isolated Enterobacteriaceae from Urinary Tract Infections. Probiotics Antimicrob Proteins. 2016;8:41-5 pubmed publisher
    ..revealed the presence of high levels of antimicrobial resistances to ceftriaxone and low levels of resistance to cephalexin. Supernatant of N...
  44. Paul J. Bullous pemphigoid in a patient with psoriasis and possible drug reaction: a case report. Conn Med. 2004;68:611-5 pubmed
    ..challenges because of the patient's concomitant history of psoriasis and apparent dermatologic reaction to cephalexin. Though the patient's skin lesions resolved rapidly with appropriate treatment, the case generated many ..
  45. Valent A, DeArmond C, Houston J, Reddy S, Masters H, Gold A, et al. Effect of Post-Cesarean Delivery Oral Cephalexin and Metronidazole on Surgical Site Infection Among Obese Women: A Randomized Clinical Trial. JAMA. 2017;318:1026-1034 pubmed publisher
    ..The optimal perioperative antibiotic prophylactic regimen in this high-risk population undergoing cesarean delivery is unknown...
  46. Youshko M, Moody H, Bukhanov A, Boosten W, Svedas V. Penicillin acylase-catalyzed synthesis of beta-lactam antibiotics in highly condensed aqueous systems: beneficial impact of kinetic substrate supersaturation. Biotechnol Bioeng. 2004;85:323-9 pubmed
    ..and D-p-hydroxyphenylglycine amide (D-HPGA) have been developed and syntheses of ampicillin, amoxicillin, and cephalexin starting from the supersaturated homogeneous solutions of substrates were performed...
  47. Geschwind J, Kaushik S, Ramsey D, Choti M, Fishman E, Kobeiter H. Influence of a new prophylactic antibiotic therapy on the incidence of liver abscesses after chemoembolization treatment of liver tumors. J Vasc Interv Radiol. 2002;13:1163-6 pubmed
    ..These patients were divided into two groups. Patients in group one (n = 4) were administered intravenous cephalexin for prophylaxis. Patients in group two (n = 4) were administered bowel preparation and tazobactam/piperacillin...
  48. Hermida M, Otero M, Della Giovanna P, Garcia S, Cabrera H. Cutaneous vasculitis following an intradermal tattoo. J Eur Acad Dermatol Venereol. 2007;21:1268-9 pubmed
  49. Okamoto S, Hamana Y, Inoue M, Mitsuhashi S. In vitro and in vivo antibacterial activities of T-2588, a new oral cephalosporin, compared with those of other oral beta-lactam antibiotics. Antimicrob Agents Chemother. 1987;31:1111-6 pubmed
    ..T-2525 was more active in vitro than cefaclor, cephalexin, and amoxicillin against members of the family Enterobacteriaceae and Branhamella catarrhalis...
  50. Giordano P, Elston D, Akinlade B, Weber K, Notario G, Busman T, et al. Cefdinir vs. cephalexin for mild to moderate uncomplicated skin and skin structure infections in adolescents and adults. Curr Med Res Opin. 2006;22:2419-28 pubmed
    To compare the efficacy and safety of cefdinir to that of cephalexin in adolescents and adults with mild to moderate uncomplicated skin and skin structure infections (USSSI)...
  51. Yang G, Tang P, Yen C. Removal of micropollutants from municipal wastewater by graphene adsorption and simultaneous electrocoagulation/electrofiltration process. Water Sci Technol. 2017;75:1882-1888 pubmed publisher
    ..Carbon adsorption, size exclusion, electrostatic repulsion, electrocoagulation, and electrofiltration were considered as the main mechanisms for the removal of target ECs by the integrated process indicated above. ..
  52. Sonani N, Hiremath S, Dasankoppa F, Jamakandi V, Sreenivas S. Design and evaluation of gastroretentive mucoadhesive cephalexin tablets. Pharm Dev Technol. 2010;15:178-83 pubmed publisher
    The aim of this investigation was to develop gastroretentive mucoadhesive tablets of cephalexin, which will retain in the stomach for 10 h. Cephalexin, a first-generation cephalosporin, becomes ionized in intestinal pH because pKa is 4...
  53. Ivanov A, Edink E, Kumar A, Galaev I, Arendsen A, Bruggink A, et al. Conjugation of penicillin acylase with the reactive copolymer of N-isopropylacrylamide: a step toward a thermosensitive industrial biocatalyst. Biotechnol Prog. 2003;19:1167-75 pubmed
    ..PolyNIPAM-cross-linked PA retained its capacity to synthesize cephalexin from d-phenylglycin amide and 7-aminodeacetoxycephalosporanic acid...