Ampicillin vs amoxicillin

Antibiotics are a group of drugs used to treat bacterial infections in humans. Among the commonly prescribed antibiotics, ampicillin and amoxicillin are often used for similar indications. Although both the drugs belong to the same family of penicillin, they differ slightly in their chemical structures, spectrum of activity, and pharmacological properties.

Ampicillin and amoxicillin are broad-spectrum antibiotics used to treat a variety of bacterial infections, including respiratory tract infections, ear infections, urinary tract infections, skin infections, and gastrointestinal infections. They work by inhibiting the growth and multiplication of the bacteria, thereby preventing the spread and progression of infection.

Despite their similarities, there are certain differences between ampicillin and amoxicillin that affect their clinical use. For instance, ampicillin is more active against gram-negative bacteria than amoxicillin. Also, amoxicillin is more stable in acidic pH and better absorbed in the gut than ampicillin. Furthermore, amoxicillin has a slightly longer half-life and requires less frequent dosing than ampicillin.

In this article, we will compare and contrast the properties of ampicillin and amoxicillin in detail and highlight their unique features that make them different from each other.

Chemical composition

Ampicillin

Ampicillin is a semi-synthetic penicillin antibiotic with a chemical formula of C16H19N3O5S. It is a derivative of penicillin and is commonly used to treat bacterial infections such as respiratory infections, urinary tract infections, and meningitis.

The chemical structure of ampicillin contains a β-lactam ring, which is responsible for the bacterial activity of the drug. Ampicillin is more active against gram-negative bacteria than amoxicillin.

Amoxicillin

Amoxicillin is a more stable and better-absorbed form of ampicillin with a chemical formula of C16H19N3O5S. It is also a penicillin antibiotic and is commonly used to treat similar bacterial infections as ampicillin.

The chemical structure of amoxicillin is similar to that of ampicillin but contains an additional hydroxyl group (-OH) on the ring, which makes it more effective against gram-positive bacteria than ampicillin.

• Both ampicillin and amoxicillin belong to the β-lactam family of antibiotics.
• They are both administered orally and intravenously, and are available in generic forms.
• They are both effective against similar bacterial infections, but their activity against different types of bacteria differs slightly.

Mode of action

Ampicillin

Ampicillin is a broad-spectrum antibiotic that belongs to the group of penicillins. It works by inhibiting the bacterial cell wall synthesis, which is essential for the survival of bacteria. Ampicillin binds to the penicillin binding proteins (PBPs) present on the bacterial cell wall, which leads to the disruption of the formation of the bacterial cell wall, and hence kills the bacteria.

Amoxicillin

Amoxicillin is also a broad-spectrum antibiotic that belongs to the group of penicillins. It has a similar mode of action to that of ampicillin. Amoxicillin also inhibits the bacterial cell wall synthesis by binding to the PBPs, thus preventing the formation of the bacterial cell wall, and ultimately leading to bacterial death.

Both ampicillin and amoxicillin are effective against a wide range of gram-positive and gram-negative bacteria. However, amoxicillin is considered to be more effective against certain strains of bacteria than ampicillin, such as Haemophilus influenzae.

It is important to note that both ampicillin and amoxicillin are susceptible to bacterial resistance. Therefore, it is essential to use them judiciously to avoid the development of antibiotic resistance.

Indications

Ampicillin

Ampicillin is a penicillin-type antibiotic that is used to treat bacterial infections such as pneumonia, bronchitis, and urinary tract infections. It works by stopping the growth of bacteria and destroying the cell walls of the bacteria. It may also be prescribed for skin infections, typhoid fever, and bacterial meningitis.

It is important to note that ampicillin is only effective in treating infections caused by bacteria and not viral infections such as the common cold or flu.

Amoxicillin

Amoxicillin is a penicillin-type antibiotic that is used to treat a variety of bacterial infections such as ear infections, strep throat, and urinary tract infections. It works by stopping the growth of bacteria and preventing the formation of their cell walls.

In addition to treating bacterial infections, amoxicillin may also be prescribed to prevent infection in people who are undergoing certain dental or surgical procedures. It is important to note that amoxicillin is only effective in treating infections caused by bacteria and not viral infections such as the common cold or flu.

Dosage and administration

Ampicillin

Ampicillin dosage depends on the severity and nature of the infection. The usual adult dose ranges from 250mg to 500mg taken orally every 6 hours, or 1g to 2g taken orally every 4 to 6 hours. For severe infections, a higher dose of 4g taken orally every day may be necessary.

Ampicillin can also be administered by injection. The usual dose for adults is 1g to 2g given every 4 to 6 hours, or 50mg/kg to 100mg/kg given every 6 hours for severe infections.

Children's doses of ampicillin are usually calculated on a weight basis of 25mg/kg per day, divided into 4 to 6 equal doses and taken orally. Higher doses may be required for severe infections. For infants under 4 weeks old, the recommended dose is 200mg/kg divided into 4 equal doses given every 6 hours.

Amoxicillin

The usual adult dose of amoxicillin is 250mg to 500mg taken orally every 8 hours or 500mg to 875mg taken orally every 12 hours. For severe infections, doses of up to 1g every 8 hours or 1.5g every 12 hours may be required.

Amoxicillin is often prescribed for children, and the dose is calculated by weight. Children weighing less than 40kg are usually prescribed a dose of 20mg/kg per day, divided into 3 to 4 equal doses and taken orally. Children who weigh more than 40kg should be given the adult dose. The course of treatment is usually 7 to 10 days.

Amoxicillin can be taken with or without food, and it is important to take the full course of medication as prescribed to make sure the infection is fully treated.

Side effects

Side effects of Ampicillin

Ampicillin can cause common side effects such as:

• Rash
• Itching
• Nausea
• Vomiting
• Diarrhea
• Heartburn

In rare cases, severe side effects can occur, including:

• Allergic reactions
• Blood disorders
• Kidney problems

Side effects of Amoxicillin

The following side effects are common with amoxicillin:

• Diarrhea
• Nausea
• Vomiting
• Rash
• Headache

More serious side effects of amoxicillin include:

• Allergic reactions such as hives, itching, and difficulty breathing
• Seizures
• Severe diarrhea
• Yellowing of the skin or eyes
• Dark urine

Differences in side effects between Ampicillin and Amoxicillin

The two drugs have similar side effects, but amoxicillin is less likely to cause skin rash and itching compared to ampicillin. However, amoxicillin may cause more serious side effects such as seizures and yellowing of the skin or eyes. It is important to seek medical attention if any of these side effects occur.

Drug interactions

Ampicillin interactions

Ampicillin can interact with other drugs and cause various side effects:

• Probenecid and methotrexate can increase ampilicin levels in the blood, leading to toxicity.
• Oral contraceptives can reduce the effectiveness of the antibiotic.
• Allopurinol and amoxicillin can increase the risk of a rash.

Amoxicillin interactions

Amoxicillin can also interact with other drugs and cause problems:

• Allopurinol and ampicillin can increase the risk of a rash.
• Anticoagulants like warfarin, can interact with amoxicillin and lead to increased bleeding risk.
• Birth control pills can reduce the effectiveness of the antibiotic.

It is important to inform your healthcare provider about all medications, supplements, and herbs that you are taking to avoid potential drug interactions.

 

 

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