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Aminopenicillins – Effect, Application & Risks


Aminopenicillins are antibiotics used for antimicrobial treatment. Due to the chemical extension of penicillin with an amino group on the benzyl radical, the drug group shows a broader spectrum of action than penicillin. Aminopenicillins are used as broad -spectrum antibiotics in various bacterial diseases.

What are aminopenicillins?

Aminopenicillin belongs to the group of beta-lactam antibiotics . This is structurally characterized by a four-membered lactam ring, which is formed during biosynthesis. Aminopenicillin and penicillin have the same basic structure. A substituted amino group on the benzyl radical distinguishes the two antibiotics in their chemical structure.

To produce aminopenicillin, an amino group is synthesized at the α-position of benzylpenicillin. The additional amino group leads to an extended range of action and makes aminopenicillin an effective broad spectrum antibiotic.

ß-lactams (beta-lactams) such as aminopenicillin are acid-resistant and can be administered orally. However, the antibiotic is not resistant to ß-lactamases. ß-lactamases are found in many bacteria and reduce the spectrum of action of aminopenicillin. ß-lactamase inhibitors prevent the antibiotic from being broken down. In combination with aminopenicillin, ß-lactamase inhibitors increase the spectrum of action of the antibiotic.

The aminopenicillins include the pharmaceuticals amoxicillin , ampicillin , pivampicillin and bacampicillin. Pivampicillin and bacampicillin are no longer prescribed. Amoxicillin and ampicillin are also used to treat bacterial diseases .

Pharmacological effect on body & organs

Aminopenicillin binds proteins via the ß-lactam ring. Like all ß-lactam antibiotics, the ß-lactam ring is the center of action and aminopenicillin binds identical protein structures to penicillin. The protein transpeptidase belongs to the group known as penicillin-binding proteins. The transpeptidase ensures the cross-linking of glycopeptides in a bacterial cell wall. If the enzymes are inactivated by ß-lactam antibiotics, the cross-linking of glycopeptides can no longer take place and the bacterial cell wall becomes unstable. With increasing instability, water flows into the bacterium, creates an osmotic imbalance and the bacterium bursts.ß-Lactam antibiotics such as aminopenicillin develop their bactericidal effect on bacteria that proliferate and form a cell wall. Due to the additional amino group on the benzyl residue, aminopenicillins capture more gram-negative bacteria than penicillins. Furthermore, aminopenicillins are four to ten times more potent against gram-negative bacteria than penicillins.

Bacterial species targeted by aminopenicillins include gram-positive bacteria such as enterococci , listeria , and Streptococcus faecalis. Salmonella , Shigella, Haemophilus influenzae , Escherichia coli , Proteus mirabilis and Helicobacter pylori are gram-negative bacteria that are within the spectrum of activity of aminopenicillins.

While the antibiotic is effective against 60% of Escherichia coli strains and against most strains of Proteus mirabilis, Haemophilus influenzae strains often show resistance. Bacteria that can produce ß-lactamase are resistant to ß-lactam antibiotics. The spectrum of action of aminopenicillins is expanded if a ß-lactamase inhibitor such as tazobactam is also taken.

Medicinal Application & Use for Treatment & Prevention

Aminopenicillins are broad-spectrum antibiotics and are administered in practice for the initial treatment of bacterial infections. A broad-spectrum antibiotic is always prescribed as initial treatment when the pathogen is unknown. For the exact and effective use of aminopenicillins, it is necessary to create an antibiogram and to identify the bacterial strain.

Aminopenicillins are used primarily for respiratory infections , urinary tract infections , sinusitis , middle ear infections (otitis media), bacterial endocarditis , listeriosis , epiglottitis , osteomyelitis , meningitis , and soft tissue infections.

Bacterial endocarditis is treated for enterococci infection. An aminoglycoside is administered concomitantly . Aminopenicillins are prescribed for UTIs only when Proteus mirabilis, enterococci, or E. coli are causing the infections.

The bioavailability of an aminopenicillin depends on its chemical structure. The aminopenicillin amoxicillin is preferably administered orally and is 60 to 80% absorbed enterally. The good bioavailability is related to a hydroxyl group substituted on the phenol ring (in the para position). By changing the chemical structure, amoxicillin utilizes the enteral dipeptide transporter. If, on the other hand, the aminopenicillin ampicillin is administered orally, enteral absorption is only 30%. 70% of the active substance thus remains in the intestinal lumen. This leads to undesirable side effects in the gastrointestinal area. Furthermore, the plasma level is increased only insufficiently. Ampicillin is preferably administered intravenously (iv) or intramuscularly (im) because of poor enteral absorption.

Aminopenicillins bind to albumin in the human bloodstream and are excreted renally. Research suggests that a minimal proportion of aminopenicillins are metabolized in the liver (hepatic).

Risks & side effects

Gastrointestinal side effects are common after oral intake of aminopenicillins. Pseudomembranous enterocolitis can occur in addition to diarrhea . Other side effects include seizures and sensory and motor disorders. These side effects often occur after high doses of antibiotics as a result of neurotoxic reactions and affect the central nervous system .In the case of infectious mononucleosis ( glandular fever ) or leukemia present at the same time as the infection, macular exanthems can occur as a result of aminopenicillin treatment . A serious side effect with penicillin derivatives such as aminopenicillins is anaphylactic shock .

Contraindications exist in renal insufficiency , chronic lymphocytic leukemia and penicillin allergy .


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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.