The following frequencies form the basis for the evaluation of adverse reactions: Very common: 10%; Common: 1%-<10%; Uncommon: 0.1%-<1%; Rare: 0.01%-<0.1%; Very rare: <0.01%, including isolated cases.
The incidence of adverse reactions is more common in the presence of renal and/or hepatic insufficiency or co-medication with ampicillin or amoxicillin.
Skin and hypersensitivity reactions:
Skin reactions are the adverse reactions most commonly observed (approx. 4%); they can occur at any time during treatment and may be pruritic, maculopapular, sometimes scaly, sometimes purpuric and rarely exfoliative.
Allopurinol is to be withdrawn immediately should such reactions occur. After recovery from mild symptoms, therapy may be resumed with a low dose (e.g. 50 mg/day). As required, this dose is to be increased gradually. If the skin rash recurs, the preparation should be permanently withdrawn, as severe generalised hypersensitivity reactions may occur.
Hypersensitivity reactions can manifest themselves as follows: Skin reactions accompanied by exfoliation, fever, lymphadenopathy, arthralgia and eosinophilia - such as Stevens-Johnson syndrome and Lyell's syndrome - rarely occur. Associated vasculitis and tissue reactions rarely occurring as well may be manifested in various ways, including hepatitis, interstitial nephritis and very rarely, seizures. If such reactions appear, it may be at any time during treatment, Allopurinol must be withdrawn immediately and permanently. Corticosteroids have proven beneficial for treatment.
In addition, the following observations have been made in isolated cases: Hypersensitivity reactions, which can manifest themselves - among others - as fever, skin reactions, chills and arthralgia, hepatic dysfunctions (reversible increase in transaminases and alkaline phosphatase), acute cholangitis and xanthine calculi.
If generalised hypersensitivity reactions have occurred, renal and/or hepatic dysfunctions were generally present particularly in lethal courses.
Very rarely, acute anaphylactic shock has been reported.
Reversible angioimmunoblastic lymphadenopathy has very rarely been described after withdrawal of allopurinol.
Hepatic dysfunctions, ranging from asymptomatic increase in liver values lo hepatitis (including hepatic necrosis and granulomatous hepatitis) have rarely been reported.
Nausea, vomiturition and diarrhea can occur. It should be paid attention to conscientious intake after meals together with sufficient liquid, particularly in patients with a sensitive stomach.
Blood and lymphatic system:
Isolated cases of blood count alterations such as leukopenia, leukocytosis, granulocytosis and eosinophilia have been reported in isolated cases.
The occurrence of thrombocytopenia, agranulocytosis and aplastic anemia has uncommonly been reported, particularly in patients with renal dysfunctions. An especially careful monitoring of these patient groups is therefore necessary.
In addition, the following observations have been made in isolated cases: General malaise, alopecia, angina, asthenia, ataxia, peripheral neuritis, bradycardia, diabetes mellitus, depression, furunculosis, dysgeusia, gynecomastia, hematemesis, hematuria, hyperlipidemia, hypertension, impotence, infertility, cataract, coma, headache, macular degeneration, edema, myalgia, neuropathy, paralysis, paresthesia, Quincke's edema, vertigo, somnolence, dysopia, steatorrhea, stomatitis, discolored hair, uremia.