For adult premedication in a patient with a penicillin allergy, which antibiotic dosage is described?

• A. Amoxicillin 2 g
• B. Clindamycin 600 mg
• C. Cephalexin 2 g
• D. Ampicillin 2 g

Answer: (D)

The key idea is choosing a non-penicillin antibiotic for adult premedication when there is a penicillin allergy. Ampicillin belongs to the penicillin family, so it would not be used in a penicillin-allergic patient due to the risk of an allergic reaction. The standard non-penicillin option for dental prophylaxis is clindamycin 600 mg taken about one hour before the procedure, which provides good coverage of oral bacteria without using a penicillin. Cephalexin 2 g can be considered in some cases of non-severe penicillin allergy, but it is a cephalosporin and carries a small cross-reactivity risk, so it’s not the first choice when penicillin exposure is a concern. Amoxicillin or ampicillin would be appropriate only for non-allergic patients. So, describing ampicillin 2 g for a penicillin-allergic adult does not align with standard practice; the preferred alternative dosage is clindamycin 600 mg.