From the Guidelines

Cephalexin is the recommended prophylactic antibiotic for a patient with a contaminated laceration on the hand who has a penicillin allergy.

The patient's penicillin allergy necessitates the use of alternative antibiotics, and Cephalexin is a suitable option for patients with non-severe penicillin allergies, as stated in the guidelines by the Infectious Diseases Society of America 1.
Cephalexin is effective against methicillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus pyogenes, which are common pathogens in contaminated lacerations.
The recommended dosage for Cephalexin is 500 mg four times a day (qid) orally for adults, and 25-50 mg/kg/day in four divided doses orally for children.
Other options, such as Clindamycin and Doxycycline, may also be considered, but Cephalexin is generally a more convenient and effective choice for patients with penicillin allergies, except those with immediate hypersensitivity reactions.
It is essential to note that Vancomycin is the parenteral drug of choice for treating infections caused by methicillin-resistant Staphylococcus aureus (MRSA), but it is not typically used for prophylaxis in contaminated lacerations unless there is a high suspicion of MRSA infection.

From the Research

For a patient with a contaminated laceration on the hand and a penicillin allergy, the choice of prophylactic antibiotics is crucial.
According to 2, a 2-day regimen of prophylactic antimicrobial agents, such as Cephalexin, is as effective as a 5-day regimen in preventing surgical site infections in simple traumatic contaminated wounds or lacerations.
However, the studies 3 and 4 suggest that prophylactic antibiotics may not be necessary for simple hand lacerations, and the decision to prescribe antibiotics should be based on the degree of contamination and other factors.
In the case of a penicillin allergy, alternative antibiotics such as Cephalexin or other non-penicillin antibiotics may be considered, as suggested by 2.
It is essential to note that the use of prophylactic antibiotics should be guided by evidence-based guidelines and individual patient factors, as emphasized by 5.

For patients with a penicillin allergy, it is crucial to choose an alternative antibiotic that is effective against the potential pathogens involved in the contamination.
Cephalexin, a cephalosporin antibiotic, may be a suitable option, as it has been shown to be effective in preventing surgical site infections in contaminated wounds 2.
However, it is essential to consider the patient's specific allergy and medical history when selecting an alternative antibiotic.

The decision to prescribe prophylactic antibiotics for a contaminated laceration on the hand should be based on a thorough assessment of the patient's condition, including the degree of contamination, wound size, and individual patient factors.
As emphasized by 4, the lack of clear guidelines and disparity in physician practice highlight the need for further research and evidence-based decision-making in this area.
Ultimately, the choice of prophylactic antibiotics should be guided by the best available evidence and individual patient needs, as well as consideration of potential allergies and side effects.