What Is the Difference Between Amoxicillin and Penicillin?

Although they are both members of the same family of antibiotics, there are some differences in how amoxicillin and penicillin are used. There can also be some different side effects associated with each medication, as well as some variation in the drugs that they interact with.

In this article, we will go over their similarities and where they differ so that you can be certain of what’s the difference between amoxicillin and penicillin.

What Is Penicillin?

Penicillin is derived from the penicillium fungus, and was one of the earliest medications that were shown to have antibiotic properties. It was discovered in 1928 by the Scottish scientist Dr Alexander Fleming, though it took more than a decade to enter mass production. Its discovery transformed the medical world, as it enabled many patients who would previously have died to survive their diseases.

Since then, it, along with the other antibiotics derived from it, is one of the most widely used and most successful treatments for bacterial infections. It works by preventing the bacteria from forming new cell walls, and so prevents them from growing.

The most commonly prescribed form today is Penicillin V, which has been enhanced with an increased ability to survive stomach acid. This allows it to be taken orally, unlike its progenitor, Penicillin G, which was limited to injections. Its use has declined somewhat since the advent of ‘super bugs’ that have developed a resistance to it.

What Is Penicillin Used for?

Penicillin is what’s known as a narrow-spectrum antibiotic, because it is mostly effective against a specific species of bacteria, in this case, gram-positive strains of streptococcus. It’s best used when the specific cause of an infection is known, as it can be targeted against diseases that it is known to treat.

Penicillin is approved for the treatment and prevention of the following conditions:

  • Dental infections such as pharyngitis (sore throat) and Vincent gingivitis (trench mouth)
  • Rheumatic fever
  • Chorea
  • Upper respiratory tract infections such as ear infections, sinus infections, throat infections, and pneumonia.
  • Mild skin and soft tissue infections
  • Bacterial meningitis
  • Bacterial endocarditis
  • Scarlet fever

It is also sometimes used to treat cases of anthrax infection, erysipeloid, and diphtheria. It’s not generally very effective against gram-negative bacteria or anaerobic bacteria.

What Is Amoxicillin?

Amoxicillin is a semisynthetic derivative of penicillin, which is why it shares many similarities with the original antibiotic. It was first discovered in 1958 in England and entered general usage in 1972. It’s a broad-spectrum antibiotic, meaning that it can be effective against a wide range of potential bacterial infections.

It is now one of the most commonly prescribed antibiotics, especially for children. Like penicillin, it prevents the formation of new cells in the bacteria it effects, but it is also actually able to kill bacteria that it comes into contact with.

Unlike penicillin, it is effective against a much wider range of bacteria species, including:

  • Certain strains of streptococcus
  • gonorrhoeae.
  • coli
  • pneumoniae
  • influenzae
  • mirabilis
  • Helicobacter pylori
  • faecalis
  • Non-penicillinase producing Staphylococcus spp.

It works similarly to ampicillin, yet another penicillin derivative that entered usage in 1961 and is much more resistant to stomach acid. This makes it a more effective treatment as it is more readily absorbed by the stomach lining and so more of the medicine enters your blood stream.

Amoxicillin is used to treat a large number of conditions, which include:

  • Ear, nose, and throat infections such as tonsillitis, pharyngitis, and otitis media
  • Lower respiratory tract infections such as pneumonia
  • Genitourinary tract infections
  • Acute, uncomplicated gonorrhea
  • Rhinosinusitis
  • Helicobacter pylori eradication
  • Skin and soft tissue infections

It is also sometimes used to treat anthrax infection and Lyme disease.

What’s the Wame and What’s the Difference Between Amoxicillin and Penicillin?

While they are pretty similar in many regards, due to one being derived from the other, there are some key differences between the amoxicillin and penicillin. Penicillin was the first antibiotic available, while amoxicillin is an enhanced version that came about thirty years later.

The primary difference is that penicillin is only effective against a narrow spectrum of bacterial infections, so it is best used when the cause of the infection has already been determined to be one of the gram-positive strains of streptococcus. Amoxicillin is more effective against a broader spectrum of bacteria, and so can be used to treat a wider spectrum of conditions.

Because amoxicillin and penicillin are both members of the penicillin family of antibiotics, the range of diseases that they can treat has a significant amount of crossover. The modern form of penicillin, Penicillin V, and amoxicillin, are both more resilient to stomach acid than the original form of the medication.

They are both slowly becoming less effective due to the increase in resistant strains of bacteria, as a result of their usage being so widespread, as well as from patients not completing their prescribed course.

The majority of the potential side effects are shared between both medicines. They can both cause minor rashes, vomiting, diarrhea, black hairy tongue, and an upset stomach. Amoxicillin however is more likely to cause a skin rash, while penicillin can also specifically cause nausea in some people.

They share some of the more serious potential side effects, such as watery or bloody diarrhea and allergic reactions. However, amoxicillin has a few more that can occur when using it, which include seizures, yellowing of the skin or eyes, and unusual bruising or bleeding.

Same Same, but Different

While they are very similar on the surface, amoxicillin and penicillin do have a fair number of differences that make them more useful for different courses of treatments. You don’t always want to use a broad-spectrum antibiotic like amoxicillin, as it can often kill off bacteria that aren’t harmful to your system, and thus negatively affect your microbiome.

Either way, you should always consult your physician before starting a course of antibiotics, least of all because they are only available by prescription in the United States.