August 24, 2016
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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Side Effects


Body as a Whole

The reported incidence of allergic reactions to penicillin ranges from 0.7% to 10% (see WARNINGS). Sensitization is usually the result of treatment, but some individuals have had immediate reactions to penicillin when first treated in such cases it is thought that the patients may have had prior exposure to the drug via trace amounts present in milk and vaccines.

Two types of allergic reactions to penicillin are noted clinically immediate and delayed.

Immediate reactions usually occur within 20 minutes of administration and range in severity from urticaria and pruritus to angioneurotic edema, iaryngospasm, bronchospasm, hypotension, vascular collapse and death. Such immediate anaphylatic reactions are very rare (see WARNINGS) and usually occur after parenteral therapy, but have occurred in patients receiving oral therapy. Another type of immediate reaction, an accelerated reaction, may occur between 20 minutes and 48 hours after administration and may include urticaria, pruritus and fever. Although Iaryngeal edema, laryngospasm and hypotension occasionally occur, fatality is uncommon.

Delayed allergic reactions to penicillin therapy usually occur after 48 hours and sometimes as late as two to four weeks after initiation of therapy. Manifestations of this type of reaction include serum sickness-like symptoms (ie, fever, malaise, urticarii, myalgia, arthralgia, abdominal pain) and various skin rashes. Nausea. vomiting, diarrhea, stomatitis, black or harry tongue and other symptoms of gastrointestinal irritation may occur, especially during oral penicillin therapy .

Nervous System REACTIONS

Neurotoxic reactions similar to those observed with penicillin G may occur with large intravenous doses of the peniciilinase-resistant penicillins, especially with patients with renal insufficiency.

Urogenital REACTIONS

Renal tubular damage and interstitial nephritis have been associated with the administration of methicin sodium and infrequently, with the administration of nafcillin and oxacillin. Manifestations of this reacti on may include rash, fever, eosinophilia, hematuria, proteinuria and renal insufficiency. Methicillin-induced nephropathy does not appear to be dose-related and is generally reversible upon prompt discontinuation of therapy.


Agranulocytosis, neutropenia and bone marrow depression have been associated with the use of methicin sodium and nafcillin.

Hepatotoxicity, characterized by fever, nausea and vomiting associated with abnormal liver function tests, mainly elevated SGOT levels, has been associated with the use of oxacillin.

Mild to Moderate Severe Mild to Moderate Severe
Dicloxacillin 125 mg every 6 hours 250 mg every 6 hours 12.5 mg/kg/dayb in equally divided doses every 6 hours 25 mg/kg/dayb in equally divided doses every 6 hours
b Patients weighing less than 40 kg (88 Ibs.)

Read the Dynapen (dicloxacillin) Side Effects Center for a complete guide to possible side effects


Tetracycline, a bacteriostatic antibiotic, may antagonize the bactercidal effect of penicillin and concurrent use of these drugs should be avoided.

Read the Dynapen Drug Interactions Center for a complete guide to possible interactions

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/8/2004

Side Effects

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