Developed in 1980, clarithromycin is an antibiotic used to treat various bacterial infections including strep throat, pneumonia, skin infections, H. pylori infection, and Lyme disease. It can also be used in combination with anti-ulcer medications to treat certain types of stomach ulcers. It is worth noting that this medication works by preventing bacteria from producing proteins that are essential to them. Without these proteins the bacteria cannot grow, replicate and increase in numbers. Eventually, they die or are destroyed by the immune system. When it comes to its side effects, clarithromycin can cause nausea, vomiting, headaches, and diarrhea. Besides, it has serious side effects, particularly liver problems. In fact, this antibiotic may also cause harm if taken during pregnancy.