Penicillin Allergy: Alternatives

• It has been reported that a significant percentage of patients labelled as ‘penicillin allergic’ are not truly allergic to the drug.
• As a result, penicillins are unnecessarily withheld from these patients, which may subsequently affect their clinical outcomes.

What is the True Incidence of ‘Penicillin Allergy’?

• General hypersensitivity reactions (e.g. rashes) to penicillin occur in between 1 and 10% of exposed patients but true anaphylactic reactions (which can be fatal) occur in less than 0.05% of treated patients.  
• patients who have a vague history of symptoms or gastro-intestinal intolerance are probably not truly allergic to penicillins.

Who is at risk?

• Patients with a history of atopic allergy (e.g. asthma, eczema, hay fever) are more likely to be allergic to penicillins.

Who should not be prescribed or administered penicillins?

• Individuals with a history of Type I allergy clinically recognisable by features of urticaria, laryngeal oedema, bronchospasm, hypotension or local swelling within 72 hours of administration, or development of a pruritic rash (even after 72 hours) should NOT receive a penicillin.

Alternatives

• Clinical studies suggest that the incidence of cross-reactivity to cephalosporins in penicillin-allergic patients is around 10% but this is thought to be an overestimate.
• The true incidence of cross-sensitivity is uncertain.
• Second and third generation cephalosporins are unlikely to be associated with cross reactivity as they have different side chains to penicillin.
• Patients with no evidence of Type I allergy to penicillin may be treated with any cephalosporin or beta lactam antibiotic for infections of any severity.
• Patients with symptoms suggestive of a Type I allergy should avoid cephalosporins and other beta-lactam antibiotics for mild or moderate infections when a suitable alternative exists. 
• In life threatening infections, when use of a non-cephalosporin antibiotic would be sub-optimal, consider giving, under observation, a second or third generation cephalosporin (e.g. cefuroxime, ceftriaxone, ceftazidime).  
•  If necessary seek advice from ID or Microbiology.

 
What about other types of antibiotics?

• Tetracyclines (e.g. doxycycline), quinolones (e.g. ciprofloxacin), macrolides (e.g. clarithromycin), aminoglycosides (e.g. gentamicin) and glycopeptides (e.g. vancomycin) are all unrelated to penicillins and are safe to use in the penicillin allergic patient.

What should be prescribed for truly penicillin allergic patients?

Urinary Tract Infections
Female Lower UTI	Trimethoprim or nitrofurantoin
Female Upper UTI	Co-trimoxazole + gentamicin
Male UTI	Trimethoprim or ciprofloxacin
Upper Respiratory Tract Infections
Sinusitis	Doxycycline
Tonsillitis	Erythromycin or clarithromycin
Otitis Media	Erythromycin or clarithromycin
Lower Respiratory Tract Infections
Community Acquired Pneumonia (non-severe)	Doxycycline
Community Acquired Pneumonia (severe)	IV Levofloxacin then oral doxycycline
Aspiration or Hospital Acquired Pneumonia (severe)	IV Vancomycin + metronidazole + gentamicin (and seek advice)
Aspiration or Hospital Acquired Pneumonia (non-severe)	Co-trimoxazole (+metronidazole if aspiration suspected)
Infective Exacerbation of COPD	Doxycycline
Peritonitis/Biliary Tract/Intra-abdominal Infections
Severe	IV Vancomycin + metronidazole + gentamicin (and seek advice)
Step down to oral	Cotrimoxazole
Skin Infections
Cellulitis (see separate protocol)	Doxycycline
Animal bites	Metronidazole + doxycycline
Surgical Prophylaxis	See separate protocol

Reference:

1. http://www.nhstaysideadtc.scot.nhs.uk/Antibiotic%20site/penhypers.htm