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Cloxapen Side Effects

Generic Name: cloxacillin

Note: This document contains side effect information about cloxacillin. Some of the dosage forms listed on this page may not apply to the brand name Cloxapen.

Applies to cloxacillin: oral capsule, oral powder for reconstitution


Common gastrointestinal complaints include nausea, vomiting, and diarrhea. Rarely the use of cloxacillin (the active ingredient contained in Cloxapen) has been associated with pseudomembranous colitis.[Ref]


Hematologic adverse effects include neutropenia, leukopenia, and thrombocytopenia. Neutropenia has occurred in 17% of patients and occurs most commonly with higher doses and longer durations of therapy. Neutropenia occurs most often after 14 days of therapy and is reversible upon discontinuation.[Ref]


Hepatic side effects include transient increases in serum transaminases and the development of cholestatic hepatitis. Liver transaminases may take several weeks to return to normal following discontinuation of therapy. Frequent monitoring of liver function tests is recommended in patients with liver disease.[Ref]


Hypersensitivity reactions include rash, fever, eosinophilia, pruritus, fever, chills, and myalgias.[Ref]


1. Pusponegoro EH, Wiryadi BE "Clindamycin and cloxacillin compared in the treatment of skin and soft-tissue infections." Clin Ther 12 (1990): 236-41

2. Westerman EL, Bradshaw MW, Williams TW "Agranulocytosis during therapy with orally administered cloxacillin." Am J Clin Pathol 69 (1978): 559-60

3. Olaison L, Alestig K "A prospective study of neutropenia induced by high doses of B-lactam antiobiotics." J Antimicrob Chemother 25 (1990): 449-53

4. Clotet B, Vea AM, Rubies-Prat J, Sala MF "Cloxacillin-induced leukopenia." Arch Intern Med 145 (1985): 1531

5. Neftel K, Muller MR, Hauser SP, Walti M, de Weck AL "More on penicillin-induced leukopenia." N Engl J Med 308 (1983): 901-2

6. Shah I, Kumar KS, Lerner AM "Agranulocytosis associated with chronic oral administration of cloxacillin for suppression of staphylococcal osteomyelitis." Am J Hematol 12 (1982): 203-6

7. Pascual J, Orofino L, Marcen R, Quereda C, Ortuno J "Cloxacillin-induced cholestasis in a renal allograft patient with chronic hepatitis." Am J Gastroenterol 85 (1990): 335-6

8. Olsson R, Wiholm BE, Sand C, Zettergren L, Hultcrantz R, Myrhed M "Liver damage from flucloxacillin, cloxacillin and dicloxacillin." J Hepatol 15 (1992): 154-61

9. Lotricfurlan S, Lejkozupanc T, Jereb M "Cloxacillin-induced cholestasis." Clin Infect Dis 19 (1994): 981-2

Some side effects of Cloxapen may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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