First of all, about the solvent of penicillin. Using benzyl alcohol to prepare penicillin injection can not only reduce the titer of penicillin by 30%, but also cause gluteal muscle induration and contracture, which affects the function of lower limbs and is not suitable for use. At present, the commonly used solvent for penicillin is compound lidocaine hydrochloride injection (composed of sodium chloride and lidocaine hydrochloride). 4ml compound lidocaine hydrochloride injection can dissolve 800 ~10.6 million units of penicillin sodium for intramuscular injection, which can not only dissolve penicillin well, but also avoid or alleviate the pain when intramuscular injection of penicillin. Second, the skin test of penicillin. As we all know, in order to prevent the allergic reaction of penicillin, especially anaphylactic shock, the Pharmacopoeia of our country stipulates that skin test must be done before using penicillin. Penicillin skin test plays an important role in predicting anaphylactic shock, but negative skin test cannot rule out the possibility of allergic reaction. Penicillium thiazole-polylysine, benzylpenicillin sodium thiazole or penicillin can be used as skin test solution, which can detect antibodies to major and minor determinants of allergic reactions with high accuracy and safety, but the former two are lacking in China at present. We usually use penicillin G sodium, which is dissolved in 0.9% sodium chloride injection to make a solution of 500 units/ml. Sterile operation, 4℃ can be used for one week, room temperature can only be used on the same day. You can also directly buy penicillin skin reagents produced by manufacturers. Each commercial penicillin skin reagent contains 2500 units of penicillin sodium. When in use, it is dissolved and diluted with 5ml sterilized physiological saline, and injected intradermally with 0. 1ml. After 20 minutes, symptoms such as local redness, pseudopodia, pitch diameter exceeding 1cm, dizziness, chest tightness and itching all over the body are positive. In addition, it is also feasible to write a skin test with any kind of penicillin (optional concentration is 300 μ g/ml). As for whether it is necessary to do a skin test again to replace penicillin from the same manufacturer with different batches or manufacturers, we believe that if the penicillin you use is produced by a manufacturer that has passed GMP certification and meets the requirements of Pharmacopoeia, it is not necessary to do a skin test again when changing batches or manufacturers. The reason is that the problem of penicillin allergy has been clarified by Chinese scientists after 20 years of research: first, penicillin is not an allergen, and allergic reaction is caused by impurities such as penicillium thiazole introduced in the production and synthesis process; Second, the impurity content is positively correlated with allergic reaction; Third, controlling the impurity content can control the occurrence of allergic reactions. The new technology to control the impurity content of penicillin has been adopted by many pharmaceutical companies at home and abroad, so as long as your medicine is produced by a GMP-certified manufacturer, meets the requirements of the Pharmacopoeia and has qualified quality, you don't have to do a skin test because of different batch numbers or manufacturers in the process of continuous medication. The commercial penicillin skin reagent and penicillin preparation are not products of the same manufacturer and batch number, but they are also officially produced and used with the approval of the state. In order to avoid the occurrence of adverse reactions, patients should be asked about their medication history and allergic reaction history before using penicillin, and those who have not used penicillin within 3 days should be given penicillin skin test. Even if the skin test is negative, allergic reactions may occur during the medication, so we should closely observe and use it with caution, and be prepared to rescue serious adverse reactions. Thirdly, about the combined use of penicillin G sodium and ampicillin. In recent years, due to the development of a new generation of penicillins and cephalosporins, the antibacterial spectrum of β -lactams has gradually expanded, so some scholars have tried to use the combination of two β -lactams (one penicillin and one cephalosporin) instead of the combination with aminoglycosides to reduce the ototoxicity and nephrotoxicity of the latter. However, the result of this new combination may be that a β -lactam drug induces bacteria to produce β -lactamase, thus destroying the effect of another drug, or it may be antagonistic because of competing for the same protein binding point. Therefore, the synergistic effect of two kinds of β -lactam drugs is often less than the combined effect of β -lactam drugs and aminoglycosides. Most people advocate the combination of β -lactams and β -lactamase inhibitors, such as amoxicillin+clavulanic acid, cefoperazone+sulbactam, or the combination of two β -lactams with different pbp, such as mezlocillin and other β -lactams. The combination of penicillin and ampicillin in the treatment of Gram-positive bacterial infection has no synergistic effect because of the similar action sites. For the treatment of gram-negative bacterial infection, penicillin can not increase the antibacterial activity of ampicillin. Therefore, this combination is of little practical significance in clinic, but it is easy to lead to bacterial drug resistance, which is neither economical nor practical.