Question 5

Cephalexin warrants caution with respect to cross-sensitivity to penicillin.

Cephalexin is a cephalosporin antibiotic that can exhibit cross-sensitivity in individuals who are allergic to penicillin. This caution is due to the structural similarities between penicillins and cephalosporins.

A) Doxycycline

Doxycycline is a tetracycline antibiotic and does not share a structural similarity with penicillin, thus it does not warrant caution regarding cross-sensitivity. Patients with penicillin allergies can typically take doxycycline without concern for allergic reactions related to penicillin.

B) Cephalexin

Cephalexin is a cephalosporin antibiotic, which can lead to cross-sensitivity reactions in patients with a history of penicillin allergy. This is primarily due to the beta-lactam ring structure that is common to both drug classes, making caution necessary when prescribing cephalexin to those with penicillin allergies.

C) Clindamycin

Clindamycin belongs to the lincosamide class of antibiotics and does not have structural similarities to penicillin. Therefore, it does not require caution for cross-sensitivity in patients allergic to penicillin.

D) Metronidazole

Metronidazole is an antibiotic that is not related to penicillin in terms of structure or mechanism of action. As such, it does not warrant caution regarding cross-sensitivity for those with penicillin allergies.

Conclusion

Cephalexin is the only medication listed that requires caution for patients with penicillin allergies due to its structural similarities with penicillin. The other options, including doxycycline, clindamycin, and metronidazole, do not pose a risk of cross-sensitivity, making them safer alternatives for individuals with penicillin allergies. Therefore, cephalexin is definitively the correct answer in this context.