Final answer:
Penicillins may cause CNS toxicity if they cross the blood-brain barrier, which can happen in conditions like meningitis or during severe allergic reactions. They exert antibacterial effects by inhibiting the transpeptidase enzyme necessary for cell-wall synthesis in bacteria. The related antibiotics, cephalosporins, also inhibit cell wall synthesis but have a structure more resistant to enzymatic breakdown.
Step-by-step explanation:
Penicillins and CNS Toxicity
Penicillins can cause CNS toxicity by inadvertently breaching the blood-brain barrier, especially in the presence of inflammation, such as meningitis. This is because when the blood-brain barrier is compromised, penicillin can enter the CNS and potentially lead to neurotoxic effects. Also, individuals who are allergic to penicillin could experience severe reactions like anaphylactic shock, which can lead to CNS complications, including coma. Allergic reactions to penicillin are considered serious and can be life-threatening.
Penicillins function by inhibiting the enzyme transpeptidase, crucial for bacterial cell wall synthesis. This inhibition causes cell lysis in bacteria, which is how penicillin exerts its antibacterial effects. However, penicillin G, the first widely used penicillin, cannot be administered orally due to its instability in the acidic stomach environment, whereas other oral penicillins like penicillin V, ampicillin, and amoxicillin are acid stable and can be given by mouth.
Among antibiotics, cephalosporins have a structure and mode of action similar to penicillins. They work on bacterial cell wall synthesis inhibition, too, but with a different background structure that includes a six-member ring fused to the ß-lactam ring. This structure gives cephalosporins the ability to withstand enzymatic breakdown by ß-lactamases more effectively compared to penicillins. Both classes of antibiotics can contribute to CNS effects if improperly introduced into the system or in cases of hypersensitivity reactions.