Which drug is known to increase the concentration of lidocaine in the blood?

Propranolol is known to increase the concentration of lidocaine in the blood due to its influence on drug metabolism and clearance. Lidocaine is primarily metabolized in the liver, and propranolol, as a non-selective beta-blocker, inhibits certain metabolic pathways, which may lead to decreased clearance and higher plasma levels of lidocaine.

When certain drugs like propranolol are administered, they can affect liver enzyme activity, specifically the cytochrome P450 system, which is responsible for metabolizing many drugs, including lidocaine. Increased levels of lidocaine can lead to enhanced effects or toxicity, emphasizing the importance of monitoring and possibly adjusting lidocaine dosages when taken concurrently with propranolol.

Other choices do not have the same effect on lidocaine metabolism. Aspirin, ibuprofen, and acetaminophen do not significantly interact with the metabolic pathways of lidocaine or impact its concentration in the bloodstream. Thus, propranolol stands out as the correct answer in this context.