Final answer:
Alternative antibiotics can be used as prophylaxis in patients allergic to penicillin, such as ampicillin, nafcillin, and gentamicin. Penicillin remains the drug of choice for treating syphilis.
Step-by-step explanation:
In patients requiring prophylaxis and are allergic to penicillin, alternative antibiotics can be used to prevent infections. Some common alternatives include ampicillin, nafcillin, and gentamicin, which are often used in combination to provide synergistic coverage against Staphylococcus and Streptococcus bacteria. In cases of syphilis, penicillin is the drug of choice, but if patients are allergic, other antibiotics may be used, although they may be less effective and require retesting for syphilis after treatment to ensure a cure.