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Tegopen Side Effects

Generic name: cloxacillin

Medically reviewed by Last updated on May 9, 2024.

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

Applies to cloxacillin: oral capsule, oral powder for reconstitution.


Take all of the cloxacillin that has been prescribed for you even if you begin to feel better. Your symptoms may begin to improve before the infection is completely treated.

Do not break, chew, open, or crush the capsules. Swallow them whole.

Cloxacillin may decrease the effectiveness of birth control pills. Use a second method of birth control while taking cloxacillin to protect against pregnancy.

If you experience any of the following serious side effects, stop taking cloxacillin (the active ingredient contained in Tegopen) and seek emergency medical attention:

Other, less serious side effects maybe more likely to occur. Continue to take cloxacillin and talk to your doctor if you experience

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

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 Tegopen) 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 (1990) "Clindamycin and cloxacillin compared in the treatment of skin and soft-tissue infections." Clin Ther, 12, p. 236-41

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

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

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

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

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

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

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

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

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.