But for the last decade, most offices and labs have been using a rapid strep test based on detecting RNA or a protein antigen of the bacterium. Rapid tests take only a few minutes but are usually performed in batches once or twice a day, to ensure consistency and accuracy. Penicillin is the best and most inexpensive way to treat strep throat. It is given orally as a liquid or tablet two or three times daily for 10 days or, occasionally, as an injection. Other antibiotics are effective for children who can't take penicillin, but they are much more expensive and in general offer no advantage over penicillin.
Children begin to feel much better within hours of receiving the first dose of antibiotic.
After three or four doses, they are not considered contagious and can usually return to school or day care. Even though the child will feel fine in just a few days, it is very important to treat strep throat for the full 10 days for which most antibiotics are prescribed. Not only does the antibiotic kill the strep bacteria, but treatment also prevents rheumatic fever, a rare but nonetheless very serious complication of strep throat. Rheumatic fever is an immunologic reaction to untreated strep throat and other strep infections, including scarlet fever. It is associated with fever, joint irritation and, most importantly, inflammation of the valves of the heart.