Mechanism
penicillin can inhibit the synthesis of bacterial cell wall, leading to the production and activation of autolysis enzymes, resulting in bacterial death. For this group of drugs, different varieties target on different penicillin-binding proteins and enzymes with these proteins and enzymes being involved in bacterial cell wall metabolism.

Indications
they have bactericidal effect during the reproduction period of bacteria. Gram-positive cocci: Streptococcus, pneumococcus, sensitive staphylococcus; and some kinds of gram-negative cocci: to Neisseria meningitidis, Neisseria gonorrhoeae, they have strong antibacterial effects. Clostridium bacilli: Corynebacterium diphtheriae; spirochete, Treponema pallidum, borrelia recurrentis, and Leptospira; they are also applicable to various kinds of inflection diseases caused by Clostridium bacillus, Tetanus bacilli, Clostridium welchii and actinomycetes; for example, various kinds of suppurative skin disease, skin bacterial infections, gonorrhea, syphilis and so on.

Contraindications
patients who are allergic to penicillin and have a history of allergy should be disabled.

Adverse reactions
1. Allergic reaction
2. Gastrointestinal discomfort.

Precautions
1. Probenecid can block the excretion of penicillin drugs with combination usage can cause the increase of its plasma concentration.
2. Before drug administration, people must be subject to skin test according to the provisions. Patients who are allergic to the procaine should be disabled from using the procaine penicillin.
3. Procaine penicillin can occasionally cause a specific reaction. Upon injection of drugs or after 1 ~2min, patients may get a series of symptoms such as feeling uncomfortable in the heart, getting endangered fear, dizziness, palpitations and auditory hallucinations. Generally there are no breathing disorders and circulatory disorders occurring. For the majority of cases can be elevated blood pressure. Generally this doesn’t require special treatment. The symptoms will be automatically relived after 1 ~ 2h. Application of sedatives and antihistamines can help to restore.
4. Low-dose of penicillin does not cause toxicity. Large doses of application may cause neuropsychiatric symptoms. For patients with hemagglutination defects, high-dose of penicillin can disrupt the blood clotting mechanism, thereby leading to bleeding tendency.
5. The aqueous solution of penicillin sodium and potassium salt are unstable, thus should be used now with.