Approximately 5% of patients can be expected to experience adverse reactions. These are mainly dose dependent. Anaphylactoid reactions are uncommon and include urticaria, rashes, itching, nausea and shivering. Administration must be stopped immediately when signs of an anaphylactoid reaction are observed. Acute, severe anaphylactoid reactions are very rare. They usually occur within the first few minutes of administration and are generally characterised by the sudden onset of respiratory difficulty and/or cardiovascular collapse; fatalities have been reported.
Delayed reactions are well described and may be severe. They are characterised by arthralgia, myalgia and sometimes fever. The onset varies from several hours up to four days after administration. Symptoms usually last two to four days and settle spontaneously or following the use of simple analgesics. Exacerbation of joint pain in rheumatoid arthritis can occur. Local reactions reported are soreness and inflammation at or near injection site and local phlebitic reaction.
Local complications at the injection site after intramuscular injection such as staining of the skin, bleeding, formation of sterile abscesses, tissue necrosis or atrophy and pain are observed. (See Table 2.)
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