Assess the patient for signs of systemic toxicity, e.g. unresolved or worsening fever, hypotension, tachycardia and
vomiting. Patients with red flags should be referred to hospital.
Red flags for hospital admission
It is recommended that patients with cellulitis and any of the following features should be referred to hospital; a
lower threshold for referral is appropriate for young children, e.g. aged less than one year, and frail older people:13
- Signs of systemic involvement or haemodynamic instability, e.g. tachycardia, hypotension, severe dehydration
- A progressing infection despite prior antibiotic treatment, e.g. spreading margins or worsening lymphangitis
- Pain suggestive of necrotising fasciitis, e.g. the patient appears in severe pain or describes their pain as rapidly
and dramatically worsening
- Unstable co-morbidities that may complicate the patient’s condition, e.g. diabetes, vascular disease or heart failure
- Immunosuppression, e.g. a history of immunodeficiency illness, currently undergoing chemotherapy or taking immunosuppressant
medicines such as prednisone, methotrexate, ciclosporin
- An animal or human bite wound requiring surgical debridement
- A large abscess formation requiring general surgical drainage
- Orbital involvement unless cellulitis is very mild
All patients with cellulitis should rest and elevate any affected limb. Antibiotics and elevation will generally reduce
any discomfort the patient is experiencing. If analgesia is required, paracetamol is preferred over non-steroidal anti-inflammatory
drugs (NSAIDs) (see: “Necrotising fasciitis”).10 A line drawn around the leading edge of the erythematous
area allows the progress of the cellulitis to be easily monitored.
Antibiotics with an appropriate spectrum of antimicrobial activity are the mainstay of treatment; these need to penetrate
soft tissue and be prescribed in doses that are sufficient and frequent enough to achieve a sustained therapeutic concentration
at the site of infection. Intravenous antibiotic treatment may be required initially to achieve a response, and may be
available via a DHB community-based programme.
If a cut, bite or abrasion is suspected to be the cause of the cellulitis the patient’s tetanus status should be checked
and a booster given if necessary. If a patient presents to general practice with cellulitis that is secondary to an injury
then it may be appropriate for an Accident Compensation Corporation (ACC) claim to be lodged.
Trial oral antibiotics first in patients with mild to moderate cellulitis
Flucloxacillin has traditionally been the first-line oral antibiotic for patients with cellulitis because all S.
pyogenes and other related streptococci are susceptible to treatment with flucloxacillin, as are approximately
90% of strains of S. aureus (i.e. all S. aureus except for MRSA), and because it is a narrow
spectrum antibiotic that penetrates skin and soft tissue well.1, 4 The importance of treatment adherence
should be discussed, and patients advised to take oral flucloxacillin at least 30 minutes before eating.14 Microbiological
swabbing of patients with cellulitis is not generally required before beginning treatment unless there are risk factors
for MRSA. Due to a lack of trials there is uncertainty as to the optimal duration of antibiotic treatment for cellulitis;15 treatment
recommendations provided may range from five to ten days.
It is recommended not to prescribe oral amoxicillin clavulanate in primary care for patients with cellulitis. Patients
with cellulitis in the facial or periorbital region should be referred to secondary care due to the risk of vision loss.
Antibiotic treatment regimens for children with cellulitis
A child with early and mild cellulitis can be trialled on oral antibiotics for five days with review by a general practitioner
after 24–48 hours.16
Flucloxacillin is recommended first-line. The Starship Children’s Health recommended regimen for oral flucloxacillin
for children with cellulitis is:16
- Flucloxacillin 10–25 mg/kg/dose, orally, three times daily, for five days (maximum 500 mg/dose) (some regimens recommended
dosing four times daily)
Flucloxacillin syrup may be unpalatable to some children therefore capsules are recommended in preference to syrup for
children who are able to swallow them.
Erythromycin can be prescribed as an alternative for children with a confirmed significant allergy to flucloxacillin.
The Starship recommended regimen is:16
- Erythromycin 20 mg/kg/dose, orally, twice daily, or 10 mg/kg/dose, orally, four times daily for five days (maximum 500
If neither flucloxacillin syrup nor erythromycin are tolerated then cefalexin oral liquid, a broader spectrum antibiotic,
is an alternative for children. The Starship recommended regimen is:16
- Cefalexin 20 mg/kg/dose, orally, twice daily, for five days (maximum 500 mg/dose)
N.B. An alternative regimen is cefalexin 12.5 mg/kg/dose, four times daily.17
Antibiotic treatment regimens for adults with cellulitis
Flucloxacillin is also the first-line recommended oral antibiotic treatment for cellulitis in adults. The recommended
regimen from the Auckland DHB Adult Empirical Antibiotic Treatment Guidelines is:18
- Flucloxacillin 500 mg, orally, four times daily, for five days
Several protocols suggest that flucloxacillin up to 1 g, orally, four times daily, for five days may be more appropriate
for some adult patients, e.g. those with moderate to severe cellulitis, patients who may not respond to lower doses of
antibiotics due to vascular co-morbidities, e.g. diabetes or peripheral vascular disease, or patients in whom the complications
of infection may be severe, e.g. those who are immunosuppressed.19 In some patients, e.g. an older patient
with low body weight and reduced renal function, it may be appropriate to initiate treatment at a reduced dose, e.g. flucloxacillin
250 mg, four times, daily.
Erythromycin can be prescribed as an alternative for adults with a confirmed significant allergy to flucloxacillin:17
- Erythromycin 800 mg, orally, twice daily, or 400 mg, orally, four times daily, for five days
Managing patients who have not responded to treatment
The natural history of cellulitis means that patients may experience an increase in erythema and swelling within the
first 48 hours of treatment. In most patients a reduction in pain in the affected skin and an improvement in appetite
and level of energy are clear signs that the infection is being brought under control despite the area of erythema remaining
unchanged or enlarging.
Treatment adherence, including the need to rest and elevate affected limbs, should be assessed in all patients who are
not responding as well as expected; the four times daily dosing of flucloxacillin can be hard for some patients to remember
or patients who have been instructed to take the antibiotic before eating may skip doses if they miss a meal. It may be
appropriate to reconsider the diagnosis in a patient who is adhering with treatment, but is not responding. If their overall
condition deteriorates, e.g. fever or tachycardia increases, referral to hospital or a change in antibiotic treatment
may be appropriate. Patients should be discussed with a paediatrician or infectious diseases physician.
Patients with mild cellulitis who are adhering to antibiotic treatment but not responding sufficiently after 48 hours
may be candidates for community-based IV treatment (see below) or an adjustment of the dosing regimen may be an alternative
option. For example, a higher oral dose taken less often may be effective, e.g. flucloxacillin 1 g, three times daily
may maintain therapeutic levels of antibiotic.
The possibility that infection is due to MRSA or another organism resistant to standard treatment should also be considered
if the patient’s condition is not improving; microbiological swab and culture may be beneficial in this situation; if
performed, details of current antibiotic treatment should be provided to the laboratory. If MRSA is isolated from swabs
co-trimoxazole is the preferred antibiotic, unless susceptibility results suggest otherwise, at the following doses:16,
- Children aged over six weeks: co-trimoxazole 0.5 mL/kg oral liquid (40+200 mg/5 mL), twice daily, for five to seven
days (maximum 20 mL/dose)
- Adults and children aged over 12 years: co-trimoxazole 160+800 mg (two tablets), twice daily, for five to seven days
N.B. Co-trimoxazole should be avoided in infants aged under six weeks due to the risk of hyperbilirubinaemia.17
If a patient has moderate cellulitis that is not responding to oral antibiotic treatment, referral to hospital should
be considered. In some situations hospital staff may decide the community-based IV antibiotic treatment is appropriate
for the patient.
When to consider community-based intravenous treatment
If a patient presents with severe cellulitis or has not responded satisfactorily to oral antibiotics then community-based
IV antibiotic treatment may be appropriate, if red flags are absent. This involves a cannula being inserted and left in
situ until the patient has completed the IV course of antibiotics. DHB protocols vary as to who is responsible
for the day-to-day care of patients with cellulitis receiving IV treatment, which includes: prescribing, administering
the IV antibiotic (and probenecid if indicated), IV line and cannula care, monitoring response to treatment (see: “Local
protocols may differ”). In some DHBs practices are supplied with “cellulitis kits” and the primary care team has responsibility
for care, in other areas IV antibiotic treatment is initiated in primary care and then continued by a district nurse,
while in other DHBs a district nurse may be responsible for care following a hospital referral from general practice.
Regardless of local protocols, the patient’s individual circumstances are always important when considering if community-based
IV antibiotic treatment is appropriate:
- Is the patient mentally and socially able to receive community-based treatment?
- Are there contraindications to providing the patient with readily accessible intravenous access – is the patient at
risk of using the IV line for recreational drug use?
- Does the patient have family members at home to assist them?
- Can the patient be monitored at least daily?
- Can the patient return to the practice if their condition deteriorates, e.g. do they have ready access to a car?
- Can the patient easily contact medical services, e.g. do they have a phone?
Cefazolin, 2 g IV, once daily, with probenecid, 500 mg orally, twice daily, is recommended by many DHBs
as the most appropriate community-based IV treatment for adult patients with cellulitis.13, 19 This regimen
is preferred as it is the most studied and it is a once daily injection whereas intravenous flucloxacillin requires either
four times daily IV administration or the use of a central line and a pump or infusor device to enable continuous infusion.
Cefazolin is subsidised for the treatment of cellulitis, but only when it is prescribed in accordance with an approved
DHB protocol and is endorsed by a general practitioner or secondary care prescriber for this purpose.
The dose of cefazolin may need to be reduced in patients with renal impairment, e.g. a creatinine clearance < 55
Probenecid is given as a 500 mg tablet, twice daily, as an adjunctive treatment in the management of
cellulitis with IV antibiotics.13 Probenecid is contraindicated in patients with a history of blood disorders,
nephrolithiasis and during an acute attack of gout.14 Because of its mechanism
of action, probenecid has a number of significant drug interactions:
- Any patients taking methotrexate should be monitored closely for symptoms of toxicity; methotrexate dose reductions
- Low dose aspirin for cardiovascular indications is not likely to be affected by probenecid, but patients should not
use aspirin in analgesic doses
- Carbapenem antibiotics, that may be used in hospital, may require dose adjustment
Probenecid should be avoided in patients with an eGFR < 30 mL/min/1.73m2.14 Patients taking
probenecid should be advised to ensure they are drinking 2 – 3 L of fluid daily to prevent the formation of urinary stones.14
Patients receiving IV antibiotics for cellulitis can be expected to show significant clinical improvement after two
to three days;22 at which time they can be switched to oral antibiotics, e.g. flucloxacillin. If the patient
has not shown any clinical improvement after this time then it is recommended that they be referred to hospital for further
assessment or discussed with an infectious disease consultant.