Amoxicillin vs Penicillin: The Comparative Analysis

Bacterial infections are one of the most common infections that occur in humans. There are a lot of different drugs that are used to treat bacterial infections of all kinds. These are called antibiotics. One of the first antibiotics to be discovered was Penicillin, which was derived from a certain type of fungi. The invention of Penicillin was a major innovation in the world of medicine and ever since then many different kinds of antibiotics have been created. Some of the antibiotics have been derived from Penicillin itself and one of them is Amoxicillin. Amoxicillin is an improved version of Penicillin that targets a wider range of bacteria and is widely used all over the world now. In this article, we will focus on the uses, side effects and comparison of Amoxicillin and Penicillin.

What are Amoxicillin and Penicillin?

Amoxicillin and Penicillin are antibacterial medicines that are given to the patients suffering from bacterial infections. Both these drugs are used to treat a huge variety of bacterial diseases. Some of the most common diseases treated with Amoxicillin and Penicillin are: respiratory tract infections, urinary tract infections, scarlet fever, tooth infections and ulcers. There are many other ways in which these are used. Although Amoxicillin is a more widely-used drug because of its obvious much-improved structure, Penicillin still works better in cases of some bacterial infections.

Side Effects

We have discussed the major uses of Penicillin and Amoxicillin that include the treatment of bacterial infections by killing the bacteria in the body. However, every medicine has its side effects. The side effects of Amoxicillin and Penicillin are almost similar because they are developed from the same type of fungi and have the same mechanism and effects on the body. The adverse effects vary from mild to severe. Some of the common side effects are as follows:

  • Breathing difficulty: A lot of people experience breathing difficulty after they take Amoxicillin or Penicillin. This might be caused by an overdose or an allergic reaction to the drug.
  • Rashes and hives: Allergic symptoms often include rashes and itching. Also, hives might be seen on the skin. Consult the doctor if you encounter this side effect and it doesn't end on its own after some time.
  • Swollen lips and tongue: If the allergic reactions become even more serious, the symptoms such as swelling of lips and tongue can be seen. In this case immediately tale antihistamines and consult your doctor.
  • Severe diarrhea: Mild diarrhea might be normal when taking these antibiotics. However, severe diarrhea and watery stool can be really harmful. This might last for about four weeks if not treated immediately. Go to the doctor if your condition worsens. In addition to this, drinking lots of fluids and electrolyte solution is necessary. If you want to prevent diarrhea in the future, take the antibiotic dosage with food.
  • Jaundice: Amoxicillin or Penicillin can cause liver damage if not taken properly, and the patient might develop jaundice symptoms. This liver damage can get worse if you continue taking the medicine, so if you face jaundice, stop your antibiotic treatment and consult a doctor.

Differences between Amoxicillin and Penicillin

  • Possible uses: Both Penicillin and Amoxicillin are used to treat infections caused by various bacteria. Amoxicillin can also do the same but it targets a larger range of infectious agents. Each of these medicines is prescribed depending on the type of infection a person is suffering from. For example, Amoxicillin is the preferred drug to treat urinary tract infections, rather than Penicillin.
  • Types and price: Both of these medicines are available in a variety of forms for the ease of the users. Both are the derivatives of the same type of fungi. They come in liquid form and in tablets. The price of both of these drugs depends on the type. The generic versions always cost less than the branded ones. But in general their prices are quite comparable.
  • Dosage: Both Amoxicillin and Penicillin differ in the ways they interact with food, so the recommended dosage for both of them will vary. Amoxicillin can be taken with food since it is easily absorbed this way, and on the other hand, Penicillin has to be taken one hour before a meal or two hours after a meal for better absorption. The right antibiotic and its dose are always chosen based on the estimated effectiveness on the type of disease-causing bacteria that the patients are dealing with.
  • Structure: The structure of Penicillin and Amoxicillin is a little different. Amoxicillin is often considered as an improved version of Penicillin. This is because Amoxicillin targets a broader range of bacteria at once in comparison to Penicillin which was discovered much earlier and thus is only effective against a smaller variety of infectious agents.
  • Allergies: The allergies caused by both of these are similar. Since these are basically the same medicine with some changes, the allergies caused by one of them be similar to the other. However, the allergies caused by Penicillin are much more than that caused by Amoxicillin.
  • Prescription age: The prescription age for Amoxicillin is over the age of 5 years and the prescription age for Penicillin is over the age of 10 years. This is the reason why Amoxicillin is more widely used and preferred by parents than Penicillin.


Penicillin is one of the oldest drugs that were ever developed. It has been used for ages to treat infectious diseases. Amoxicillin is a fairly new drug that has been made by modifying Penicillin. Both of these are used in treating a variety of bacterial infections. In some cases, Amoxicillin is preferred and in some, the good old Penicillin seems to be more effective on the bacteria. Both of these medicines are relatively safe. However, it is not advised to take any of these during breastfeeding. Additionally, it is very important to take both of these drugs under medical supervision or otherwise it may lead to a lot of serious complications in the body.