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What is the best antibiotic to treat strep throat?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Nov 20, 2020.

Official Answer

by Drugs.com

Penicillin or amoxicillin are considered the best first-line treatments for Strep throat. According to the CDC (Centers for Disease Control and Prevention) “There has never been a report of a clinical isolate of group A strep that is resistant to penicillin”.

For people with a penicillin allergy, treat Strep throat with either a narrow-spectrum cephalosporin (such as cephalexin or cefadroxil), clindamycin, azithromycin, or clarithromycin. Note that resistance to azithromycin and clarithromycin has been reported.

What are the recommended dosages of antibiotics used to treat Strep throat?

Antibiotic dosages can vary depending on age and weight. The CDC recommends the following dosages of antibiotics for Strep throat, for those people without a penicillin allergy. One dosage regimen should be chosen that is appropriate for the person being treated.

Oral Penicillin V

  • Children: 250mg twice daily or 250mg three times daily for 10 days
  • Adolescents and adults: 250mg four times daily or 500mg twice daily for 10 days

Oral amoxicillin

  • Children and adults: 50 mg/kg once daily (maximum 1000mg once daily) for 10 days
  • Children and adults: 25 mg/kg twice daily (maximum 500mg twice daily) for 10 days

Intramuscular Benzathine penicillin G

  • Children <27 kg: 600 000 units as a single dose
  • Children and adults ≥27 kg: 1 200 000 units as a single dose

The CDC recommends the following dosages of antibiotics for Strep throat, for those people with a penicillin allergy. One dosage regimen should be chosen that is appropriate for the person being treated.

  • Oral cephalexin 20 mg/kg twice daily (maximum 500 mg twice daily) for 10 days
  • Oral cefadroxil 30 mg/kg once daily (maximum 100mg once daily) for 10 days
  • Oral clindamycin 7 mg/kg three times daily (maximum 300 mg three times daily) for 10 days
  • Oral azithromycin 12 mg/kg once daily for the first day (maximum 500 mg), followed by 6 mg/kg once daily (maximum 250 mg once daily) for the next 4 days
  • Oral clarithromycin 7.5 mg/kg twice daily (maximum 250 mg twice daily) for 10 days.

Are antibiotics always necessary to treat a Strep throat?

Although most Strep throats will get better by themselves, there is a risk of acute rheumatic fever and other complications (such as oral abscesses or mastoiditis [a bacterial infection in the mastoid process, which is the prominent bone behind the ear]) occurring. The CDC recommends that all patients, regardless of age, who have a positive rapid antigen detection test (RADT) (also known as the rapid streptococcal test, which detects the presence of GABHS cell wall carbohydrate from swabbed material) or throat culture receive antibiotics.

Antibiotics have been shown to:

  • Shorten the duration of Strep throat symptoms
  • Reduce the likelihood of transmission to family members, friends, and other close contacts
  • Prevent the development of rheumatic fever and other complications.

Viral sore throats should not be treated with antibiotics. Treatment is usually given for ten days and liquid antibiotics can be given to children who are unable to swallow tablets or capsules. Some patients may benefit from a single shot of penicillin intramuscularly.

What are the symptoms of a Strep throat?

Generally, Strep sore throats tend to be very painful and symptoms persist for a lot longer than sore throats due to another cause. Swallowing may be particularly difficult and painful. Symptoms of a Strep throat may include:

  • Sudden onset of sore throat
  • Very red and swollen-looking tonsils and back of the throat
  • Sometimes streaks of pus or red spots may appear on the roof of the mouth
  • A headache
  • Fever and Chills
  • Swollen and tender glands (lymph nodes) in the neck.

Children are more likely to feel sick (develop nausea) and vomit.

People with a Strep throat do NOT typically have a cough, runny nose, hoarseness, mouth ulcers, or conjunctivitis. If these symptoms occur there is more likely to be a viral cause for the sore throat.

Some people (usually children aged 4 to 8years) are susceptible to the toxins (poisons) produced by the S. pyrogenes bacteria and develop a bright red rash that feels like sandpaper to the touch. A rash caused by S. pyrogenes bacteria is known as Scarlet Fever (also called scarlatina). Although it usually follows a sore throat, it may also occur after school sores (impetigo).

How is a Strep throat diagnosed?

A throat swab taken by a doctor and then cultured in a laboratory is the only way to definitively tell if a sore throat is a Strep throat. If the result is positive, your doctor will prescribe antibiotics to prevent any complications, reduce symptoms, and prevent spread to other people.

Are Strep throats contagious?

Yes, Strep throats are contagious, and the bacteria are easily transmitted and spread by coughing or sneezing or after coming into contact with infected droplets, and then touching your mouth, nose, or eyes. Transmission of bacteria can also occur via contact with people with Scarlet fever, or other group A skin infections.

Without treatment, people with Strep throat can pass on the bacteria to others for one to two weeks after symptoms appear. The best way to prevent infection is to wash your hands often and always before eating or after being in contact with an infected person. Do not share utensils, linen, or personal items. People with Strep throat or scarlet fever should stay home for at least 24 hours after starting antibiotics or until they feel well enough to return to school or work.

What is scarlet fever?

Scarlet fever is the name given to a bright red rash that develops following a Strep throat, although it can also develop following school sores (impetigo).

Scarlet fever is less common than it was one hundred years ago because of antibiotic use and it only occurs in those who are susceptible to the toxins produced by the Streptococcal bacteria. It mostly occurs in children aged 4 to 8 years. By 10 years old more than 80% of children have developed lifelong protective antibodies against streptococcal toxins, whilst infants younger than 2 still have antibodies against the toxin that they acquired from their mother. This means that if two children in one family develop Strep throat, only one may develop scarlet fever.

Scarlet fever is a bright red rash that feels like sandpaper to the touch. The rash typically starts on the neck, underarm, or groin as small, flat red blotches that gradually become fine bumps and feel rough to the touch. In the body folds (such as in the armpits, elbows, and groin) the rash may appear a brighter red (called Pastia's lines). Facial flushing is common although a pale area may remain around the mouth. After seven days, the rash fades and some skin peeling may occur over the next month or longer, particularly around the fingertips, toes, and groin area.

Left untreated, Scarlet fever may progress to:

  • Ear, sinus, and skin infections
  • Joint inflammation
  • Rheumatic fever (an inflammatory disease that can cause permanent heart damage and also affect the brain, joints, and skin)
  • Otitis media
  • Pneumonia
  • Septicemia
  • Glomerulonephritis
  • Osteomyelitis.

In the pre-antibiotic era, death occurred in 15-20% of people with Scarlet fever. Nowadays, most people fully recover within four to five days with antibiotics.

What is Rheumatic Fever?

Rheumatic fever can develop following a Strep throat infection or scarlet fever. Although rare in the contiguous U.S., the disease is still prevalent in children of Samoan descent living in Hawaii and residents of American Samoa.

Symptoms of rheumatic fever usually show 14 to 28 days after a Strep infection. Because the bacteria trick the body's immune system into attacking healthy tissues, the disease can affect the heart, joints, skin, and brain.

Symptoms of rheumatic fever include:

  • Fever
  • Abdominal pain
  • Chest pain or shortness of breath
  • Joint swelling, pain, redness, or warmth
  • Nose bleeds
  • A rash on the upper part of the arms or legs (usually ring-shaped or snake-like)
  • Skin nodules or lumps
  • Unusual crying or laughing or quick jerky movements of the face, hands, or feet.

Rheumatic fever has the potential to cause life-long cardiac problems if not treated promptly or properly. Antibiotics are effective at preventing the disease if administered within nine days of symptoms. Children who develop rheumatic fever may need regular penicillin injections until the age of 21 or for 10 years after diagnosis.

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