Hi, Tri-Sprintec is a birth control pill, consisting of progesterone and estrogen. Besides, as a contraceptive, t also acts on the symptoms of mild to moderate form of Acne. Hence this drug is prescribed to patients, usually above 15 years of age and who have got menarche, to control the condition of acne. Doxycycline, is a good choice as an oral agent to control any bacterial infection in the blocked skin pores, resulting in mild to severe inflammatory acne. Simultaneous, use of Tri-Sprintec and Doxycycline is generally safe and without any main interaction. Still, Doxycycline may suppress some bacteria of stomach and hence, absorption of ethinyl estradiol may be decreased from stomach resulting in decreased level of ethinyl estradiol. This may decrease the efficacy of Tri-Sprintec to some extent. However, in actual practice, this effect is seen very rarely and usually not a concern for their simultaneous use. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician