<p>Occasionally, hypersensitivity reactions involving the skin (e.g. urticaria, morbilliform or scarlatiniform rashes, pruritus), eosinophilia or more serious allergic reactions, e.g. drug fever, vasculitis, serum sickness or interstitial nephritis, may develop. Anaphylactic or anaphylactoid reactions accompanied by, e.g- angioneurotic oedema, oedema of the larynx, bronchial spasm and shock may occur.<br />
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In the event of signs pointing to anaphylactic/anaphylactoid reactions, the treatment must be terminated immediately. In occasional instances, there may be skin rashes or inflammation of mucous membranes, especially in the region of the mouth (stomatitis); dryness of the mouth and disorders of taste may rarely occur.<br />
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The occurrence of severe bullous skin reactions- usually involving the mucosae- has been reported in isolated cases (Stevens-Johnson syndrome, Lyell&#39;s syndrome). Gastrointestinal disturbances with, e.g., nausea, vomiting, abdominal pain, loose stools, or diarrhoea may develop.<br />
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Diarrhoea may sometimes be a symptom of enterocolitis which may, in some cases, be haemorrhagic. A particular form of enterocolitis that can occur with antibiotics is pseudomembranous colitis (in most cases due to Clostridium diffcile). This must be considered in patients in whom severe, persistent diarrhoea occurs during treatment or in the initial weeks thereafter. Even if pseudomembranous colitis is only suspected, administration of Phenoxymethyl penicillin must be halted immediately. This type of colitis requires immediate and appropriate treatment by a physician. Drugs that inhibit intestinal peristalsis must not be taken in such cases. In isolated cases, particularly after high doses and prolonged administration, changes in blood picture such as reduction in the number of white blood cells (e.g.,leucopenia, granulocytopenia, agranulocytosis), erythrocytes (e.g., due to haemolytic anaemia), thrombocytes, or pancytopenia and myelosuppression may occur. During treatment for spirochaetal infections, Herxheimer&#39;s reaction characterized by the occurrence or worsening of general symptoms such as fever, chills, headache, and joint pains may develop. In isolated cases, drug-induced aseptic meningitis may occur.<br />
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In extremely rare cases, transient discolouration of the teeth may be seen during treatment with Phenoxymethyl penicillin. Administration of antibiotics, especially if prolonged, may lead to the proliferation of resistant micro organisms.<br />
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Beta-lactams predispose the patient to encephalopathy risk (which may include convulsions, confusion, impairment of consciousness, movement disorders), particularly in case of overdose or renal impairment.</p>