Question 19

Doxycycline is affected by calcium interactions.

Doxycycline, a tetracycline antibiotic, can form complexes with calcium ions, leading to reduced absorption and therapeutic effectiveness of the medication.

A) Azithromycin

Azithromycin is a macrolide antibiotic that does not have significant interactions with calcium. It remains effective regardless of calcium intake, making it an incorrect option in relation to the question.

B) Doxycycline

Doxycycline is indeed affected by calcium interactions; the presence of calcium can impair the absorption of doxycycline in the gastrointestinal tract, reducing its therapeutic effect. This makes it the correct answer to the question posed.

C) Doxylamine

Doxylamine is an antihistamine and does not have known interactions with calcium that would affect its therapeutic efficacy. Therefore, it is not the correct choice in this context.

D) Erythromycin

Erythromycin, another macrolide antibiotic, is not significantly influenced by calcium. Its effectiveness is not impaired by calcium interactions, rendering it an incorrect option for this question.

Conclusion

Doxycycline is the only medication listed that is negatively impacted by calcium, which can reduce its absorption and therapeutic effect. The other options, including azithromycin, doxylamine, and erythromycin, do not exhibit this interaction, confirming that they are not relevant to the question. Thus, doxycycline is definitively the correct answer.