aminopenicillin

Aminopenicillins are a subclass of penicillin antibiotics that include ampicillin and amoxicillin. They are characterized by an amino substituent on the side chain, which broadens their activity against certain Gram‑negative bacteria compared with natural penicillins while preserving activity against many Gram‑positive organisms.

Like other beta‑lactams, aminopenicillins inhibit bacterial cell wall synthesis by binding to penicillin‑binding proteins, leading to cell lysis. They are typically susceptible to hydrolysis by many beta‑lactamases, which limits their effectiveness against resistant strains; combinations with beta‑lactamase inhibitors can extend their spectrum.

The usual spectrum includes many Gram‑positive cocci (e.g., Streptococcus species and, in some cases, Enterococcus), plus several Gram‑negative organisms such as Haemophilus influenzae, Escherichia coli, and Proteus species. They have limited activity against Klebsiella, Pseudomonas, and most anaerobes. Amoxicillin/clavulanate or ampicillin/sulbactam expands coverage by inhibiting beta‑lactamases.

Pharmacokinetics differ: amoxicillin has good oral bioavailability and acid stability, with once‑daily or twice‑daily dosing, while ampicillin is less well absorbed orally. Both are primarily excreted renally and distribute into extracellular fluids; CNS penetration increases with meningeal inflammation.

Clinical use includes respiratory tract infections, otitis media, sinusitis, urinary tract infections, and skin infections. Amoxicillin is commonly used for dental prophylaxis and mild infections; adverse effects are generally mild and include rash, diarrhea, and hypersensitivity reactions. Caution is advised in patients with mononucleosis and in those with penicillin allergies.