See the DrugPatentWatch profile for doxycycline

There is no definitive scientific evidence to suggest that doxycycline, an antibiotic commonly used to treat bacterial infections, impacts the cholesterol-lowering effect of Lipitor (atorvastatin), a medication used to treat high cholesterol levels.

Both doxycycline and Lipitor are metabolized in the liver by different cytochrome P450 isoenzymes [1]. Doxycycline is primarily metabolized by CYP450 isoenzyme 3A4, while Lipitor is metabolized by CYP450 isoenzyme 3A4 and to a lesser extent by isoenzyme 2C9 [1].

Although both drugs share a common metabolic pathway, they are not expected to interact significantly, as they do not compete for the same enzymes [1]. Therefore, it is unlikely that doxycycline would impact the cholesterol-lowering effect of Lipitor.

However, it is essential to consult a healthcare professional or pharmacist before combining any medications, as individual responses to drug interactions can vary [1].

Sources:
[1] DrugPatentWatch.com. (n.d.). Doxycycline and Lipitor (Atorvastatin) Drug Interactions. Retrieved from https://drugpatentwatch.com/interactions/doxycycline-and-lipitor-atorvastatin