Discussion
This trial suggests that it is highly probable that a substantial
reduction in the number of repeat episodes of cellulitis of the
leg could be achieved by giving patients prophylactic antibiotics
for a period of 6 months after treatment of the acute episode.
The result was of borderline statistical significance (meaning
that there is an 8% chance that the observed benefits could have
occurred by chance), but has to be interpreted in the context of
a virtual absence of similar data elsewhere, the large potential
magnitude of effect, and the consistency of possible benefit for
a range of outcomes.25 The study indicates that a possible treatment
effect deserves further investigation, especially as the
intervention is low cost, safe and well tolerated by patients.
Although the PATCH II trial suggested a large treatment
effect (a 47% reduction in the risk of a repeat episode),
prophylactic penicillin did not prevent all subsequent cases of
cellulitis of the leg. This would suggest that other factors are
also important in determining whether or not a patient will
experience further episodes. This is consistent with other studies,
which report that penicillin treatment may not achieve
microbial clearance26 and that even when prophylaxis is ongoing,
some patients continue to experience further attacks.27
The findings are particularly important as they challenge two
commonly held beliefs about the management of cellulitis: (i) that
prophylactic penicillin V is warranted only in people with recurrent
cellulitis and ⁄or those who have known risk factors for repeat
attacks, such as lymphoedema; and (ii) that prophylactic antibiotics
are required long-term (or indefinitely) for benefits to be sustained.
If the findings of the PATCH II trial are replicated in other studies
then it is possible that all patients could be routinely offered a 6-
month course of low-dose penicillin V after an attack of cellulitis of
the leg. The rationale for such a treatment option is sound. Previous
researchers have demonstrated that lymph drainage is compromised
following an attack of cellulitis.28,29 It is therefore possible that a typical
7–10-day course of antibiotics during the acute phase of the infection
may not be sufficient to achieve complete microbial
clearance from the lymph system. The traditional model of giving
antibiotic prophylaxis only to patients with recurrent cellulitis, or to
those who already have chronic lymphoedema may in fact be too
late to prevent the permanent impairment to lymph drainage in the
leg that ensues following repeated episodes of cellulitis.