The Centers for Disease Control and Prevention recommends either:

Metronidazole
Erythromycin is given (orally or by injection) for 14 days (40 mg/kg per day with a maximum of 2 g/d), or
Procaine penicillin G is given intramuscularly for 14 days (300,000 U/d for patients weighing <10 kg and 600,000 U/d for those weighing >10 kg); patients with allergies to penicillin G or erythromycin can use rifampin or clindamycin.In cases that progress beyond a throat infection, diphtheria toxin spreads through the blood and can lead to potentially life-threatening complications that affect other organs, such as the heart and kidneys. Damage to the heart caused by the toxin affects the hearts ability to pump blood or the kidneys ability to clear wastes. It can also cause nerve damage, eventually leading to paralysis. About 40% to 50% of those left untreated can die. Epidemiology
Diphtheria is fatal in between 5% and 10% of cases. In children under five years and adults over 40 years, the fatality rate may be as much as 20%. In 2013, it resulted in 3,300 deaths, down from 8,000 deaths in 1990. Better standards of living, mass immunization, improved diagnosis, prompt treatment, and more effective health care have led to a decrease in cases worldwide. History
In 1613, Spain experienced an epidemic of diphtheria. The year is known as El Año de los Garrotillos (The Year of Strangulations) in the history of Spain.In 1735, a diphtheria epidemic swept through New England.Before 1826, diphtheria was known by different names across the world.
Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks more than 10% of those diagnosed with the disease may die. Signs and symptoms may vary from mild to severe and usually start two to five days after exposure. Symptoms often come on fairly gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat. This can block the airway and create a barking cough as in croup. The neck may swell in part due to enlarged lymph nodes. A form of diphtheria which involves the skin, eyes or genitals also exists. Complications may include myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low levels of platelets. Myocarditis may result in an abnormal heart rate and inflammation of the nerves may result in paralysis.Diphtheria is usually spread between people by direct contact or through the air. It may also be spread by contaminated objects. Some people carry the bacterium without having symptoms, but can still spread the disease to others. The three main types of C. diphtheriae cause different severities of disease. The symptoms are due to a toxin produced by the bacterium. Diagnosis can often be made based on the appearance of the throat with confirmation by microbiological culture. Previous infection may not protect against infection.A diphtheria vaccine is effective for prevention and available in a number of formulations.