Learn more about Ampicillin

Ampicillin is one of the most commonly-used beta-lactam antibiotics today. It was introduced in 1961 by Beecham, a British, pharmaceutical company. Ampicillin is originally branded "Penbritin", and was demonstrated to have antibacterial activity against Gram-Positive and Gram-negative microorganisms.

To better understand Ampicillin's mechanism of action, it is important to know what a beta-lactam antibiotic is, and how it suppresses bacterial growth.

Beta-Lactam Antibitoics


Beta-Lactam is a broad family of antibiotics. The group was so-called because they contain beta-lactamase inhibitor. This molecule suppresses the biosynthesis of bacterial cell wall, thus, preventing them to shift to their vegetative state. Antibiotics such as ampicillin contain a gene that codes for beta-lactamase.

Beta-lactam antibiotics can inhibit the growth of Gram-positive and Gram-negative bacteria. Bacteria are known to have a peptidoglycan cell wall which protects the cell from lysis. Beta-lactamase inhibits the formation of this peptidoglycan layer, and promoting cell lysis or death among bacteria. Beta-lactam antibiotics such as ampicillin act best against Gram-Positive bacteria, since their peptidoglycan wall is more prominent than in Gram-negative bacteria. Moreover, Gram-negative bacteria have lipopolysaccharide layer that can serve as a barrier for their petptidoglycan wall against antibacterial agents.

Once the peptidoglycan cell wall of bacteria has been ruptured, the cell can no longer undergo cell division, thus, no bacterial growth will occur.

Preparation of Ampicillin usually comes in capsules of 250 g and 500 mg in dosage. Powder oral suspension is also availabl and they come in 125 and 2 50 mg/5ml. Some brands also have powder for injection, which is available in 250 and 500 mg; 1 and 2 g.

Prior to usage, ampicillin capsules and powder should be stored at room temperature; 15 C (59 F) to 30 C (86 F). After preparation of the powder oral suspension, the mixture can be used for seven to 14 days, if properly sealed and stored.

Ampicillin is usually prescribed to treat infections in sinuses, stomach and intestines, kidney and middle ear. It can also be used in mild gonorrhea ,endocarditis and meningitis.

The usual oral dosage of Ampicillin is 250 mg to 500 mg; it should be taken every 6 hours, daily for 7-14 days. In gonorrhea infections, ampicillin can be taken up with probenecid. Probenecid will slow down the elimination of ampicillin from the body. It is also important to note that food in the stomach and intestines reduce the action of ampicillin. It should be taken 2 hours after a meal for optimal absorption.

Ampicillin is safe to take during pregnancy but it can lead to drug-related skin rashes when taken with allopurinol. For nusing mothers, ampicillin derivatives can be excreted in breast milk and may induce diarrrhea or allergic responses in nursing babies.

Common side effects of ampicillin include nausea, diarrhea, abdominal pain, loss of apetite, skin rashes, headache, dizziness and confusion. Patients with allergic reaction to penicillin should not be allowed to take ampicillin. In addition, ampicillin can increase the growth of some colon bacteria such as Clostridium difficile, which in turn can cause inflammation of the colon. If such cases occur, physician should be contacted immediately.