Penicillin and amoxicillin are the first-choice antibiotics for strep throat. According to the CDC, Group A Streptococcus (the bacteria that cause Strep throat) has never shown resistance to penicillin, making it the gold standard treatment.

First-Line Strep Throat Antibiotics (CDC recommended dosages)

Penicillin V (oral):

Penicillin V potassium is the most commonly prescribed antibiotic for strep throat. The CDC recommends the following dosage of penicillin for strep throat:

• Children: 250 mg 2-3 times daily for 10 days.
• Adolescents and adults: 250 mg 4 times daily or 500 mg 2 times daily for 10 days.

Amoxicillin:

Amoxicillin for children tastes better than penicillin V, and can also be given once a day.

• Weight based dosing: 50 mg/kg (maximum 1000 mg) 1 time a day for 10 days.
• Alternate dosing: 25 mg/kg (maximum 500 mg) 2 times a day for 10 days.

Benzathine penicillin G (IM injection):

Benzathine penicillin G (Bicillin L-A) is a single-dose intramuscular injection for strep throat.

• Weight less than 27 kg: 1 dose (600,000 U)
• Weight 27 kg or more: 1 dose (1,200,000 U).

Strep Throat Antibiotics for Penicillin Allergy (CDC recommended dosages)

In people who are allergic to penicillin, these antibiotics may be used to treat strep throat:

• Cephalexin, oral (narrow-spectrum cephalosporin)
  • 20 mg/kg/dose (maximum 500 mg/dose) 2 times daily for 10 days.
• Cefadroxil, oral (once-daily dosing)
  • 30 mg/kg (maximum 1000 mg) 1 time a day for 10 days.
• Clindamycin, oral (good for severe infections)
  • 7 mg/kg/dose (maximum 300 mg/dose) 3 times a day for 10 days.
• Azithromycin, oral (Z-pack) - 5-day course
  • 12 mg/kg (maximum 500 mg) for the first dose, then 6 mg/kg (maximum 250 mg) 1 time a day for the next 4 days.
• Clarithromycin, oral - Alternative macrolide
  • 7.5 mg/kg/dose (maximum 250 mg/dose) 2 times a day for 10 days.

⚠️ Note: Resistance to azithromycin and clarithromycin has been reported.

Are antibiotics always necessary to treat a Strep throat?

The CDC recommends antibiotics for all positive strep throat cases to prevent serious complications such as rheumatic fever and heart complications. A RADT (rapid antigen detection test - also known as the rapid streptococcal test) is used to detect the presence of GABHS cell wall carbohydrate from swabbed material and will confirm strep throat. Antibiotics have been shown to:

• Shorten the duration of Strep throat symptoms by 1 to 2 days
• Reduce the likelihood of transmission to family members, friends, and other close contacts
• Prevent the development of rheumatic fever and other complications, such as heart damage, kidney disease, or abscesses.

Internationally, some countries only treat people with strep throat at high risk of complications, such as rheumatic fever. Most cases of strep throat get better by themselves. People at higher risk of rheumatic fever include those:

• Who have had rheumatic fever before
• Who have a family member who has had rheumatic fever
• Are of certain ethnicities (such as Pasifika, African-American, Māori, Asian)
• Aged 3 to 35 years
• Who live in poorer or crowded living conditions.

Viral sore throats should not be treated with antibiotics. But it can be difficult to tell the difference between strep throat and a viral sore throat so see a healthcare provider for a strep throat test.

Strep throat symptoms

Generally, strep 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, severe throat pain
• Red swollen tonsils with white patches
• Fever and Chills
• Swollen neck lymph nodes
• Headache
• No cough or runny nose.

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 8 years, are susceptible to the toxins produced by strep bacteria and develop a bright red rash that feels like sandpaper to the touch.

• A rash caused by strep bacteria is known as Scarlet Fever (also called scarlatina).
• Although it usually follows a sore throat, it may also occur after school sores (impetigo).

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Strep Throat Complications Without Treatment

Untreated strep throat can cause:

• Rheumatic fever (an inflammatory disease that can cause permanent heart damage and also affect the brain, joints, and skin)
• Scarlet fever (sandpaper-like rash)
• Kidney inflammation (glomerulonephritis)
• Ear and sinus infections
• Pneumonia
• Blood infection (septicemia)
• Skin infections
• Joint inflammation (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.

How is a Strep throat diagnosed?

Accurate diagnosis of strep throat requires:

• Rapid strep test (RADT) - Results in minutes
• Throat culture - Most accurate, takes 1-2 days
• Clinical symptoms - Physical examination.

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 antibiotics: Contagious for 1-2 weeks after symptoms start
• With antibiotics: No longer contagious after 24 hours of treatment.

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.
• Stay home for at least 24 hours after starting antibiotics or until you feel well enough to return to school or work.

What is scarlet fever?

Scarlet fever is a strep throat complication causing a distinctive red, sandpaper-textured rash. It is most common in children aged 4-8 years old.

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.

Scarlet fever is less common than it was one hundred years ago because of antibiotic use. It only occurs in those who are susceptible to the toxins produced by the Streptococcal bacteria.

Scarlet fever symptoms:

• Bright red rash starting on neck/groin
• "Strawberry tongue" (red and bumpy)
• High fever
• Peeling skin after the rash fades.

Frequently Asked Questions

How long does strep throat last with antibiotics?

When treated with antibiotics, strep throat symptoms typically begin to improve within 24-48 hours of starting treatment, with complete recovery usually occurring within 3-5 days.

Can strep throat go away without antibiotics?

While strep throat can sometimes resolve on its own without antibiotic treatment, leaving it untreated carries significant risks of serious complications such as rheumatic fever, kidney problems, or the spread of infection to other parts of the body.

What's the fastest-acting strep throat antibiotic?

Penicillin given by injection works the fastest against strep throat, while oral antibiotics like penicillin or amoxicillin typically take 24-48 hours to show noticeable improvement in symptoms.

How do you know if strep throat antibiotics are working?

You can tell that strep throat antibiotics are working when your fever breaks and throat pain begins to decrease significantly within 1-2 days of starting treatment, indicating that the infection is responding to the medication.

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.

References

• Oakley A. Scarlet fever. DermNet NZ. https://dermnetnz.org/topics/scarlet-fever#:~:text=Scarlet%20fever%20occurs%20mostly%20in,and%20females%20are%20affected%20equally
• Clinical Guidance for Group A Streptococcal Pharyngitis. CDC. https://www.cdc.gov/group-a-strep/hcp/clinical-guidance/strep-throat.html

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