Physical and chemical properties:
Sodium salt and potassium salt are white crystalline powder; they are odorless or slightly specific odor, and have moisture absorption property; they lose efficacy quickly when they meet acid, alkali or oxidant, and aqueous solution is easy to fail when placed at room temperature. Soluble in water, soluble in ethanol, insoluble in fatty oil or liquid paraffin. Procaine benzylpenicillin is a kind of white microcrystalline powder, which can rapidly lose efficacy in the presence of acid, reducing agent or oxidant. It is soluble in methanol, slightly soluble in ethanol or chloroform and slightly soluble in water. Benzathine benzylpenicillin is a white crystalline powder. The pKa of penicillin free acid was 2.8. Penicillin sodium 0.6 μ G is 1 unit, LMG is equivalent to 1670 units. Penicillin potassium 0.625 μ G is 1 unit, LMG is equivalent to 1598 units.
Pharmacology:
It has a strong antibacterial effect on Gram-positive cocci (Streptococcus, pneumococcus, sensitive Staphylococcus) and gram-negative cocci (meningococci, gonococcus), Gram-positive bacilli (Diphtheria Bacillus), spirochetes (Treponema pallidum, Treponema retroflexum, Leptospira), Clostridium (tetanus, gas gangrene), etc Actinomycetes and some Bacteroides have antibacterial effect. Penicillin sodium and potassium are not acid resistant and have poor oral absorption. After intramuscular injection of 1 million units, the serum concentration reached the peak value at 0.5 hours, about 20 units / ml; the elimination was rapid, most of which were excreted by urine and eliminated from the body within several hours, T1 / 2 = 0.5 hours.
Indication:
Benzathine penicillin absorption is very slow, blood concentration is low, suitable for long-term use of penicillin prevention of patients, such as patients with chronic rheumatic heart disease.
Adverse reactions:
- Common allergic reactions include severe anaphylactic shock and serotype reaction, leukopenia, drug eruption, contact dermatitis and asthma attack.
- Low dose of penicillin did not cause toxicity. High dose can cause neuro psychiatric symptoms, such as hyperreflexia, disturbance of consciousness, hallucination, convulsion, lethargy and so on. It can also cause short-term mental disorder. It can be recovered by stopping or reducing the dosage. For a small number of patients with coagulation defects, high-dose penicillin can disrupt the coagulation mechanism and cause bleeding tendency.
Contraindication:
It is forbidden for those allergic to this product or other penicillins. Procaine penicillin should not be used in patients allergic to procaine.
Matters needing attention:
(1)All of the above penicillins can cause allergic reaction, and skin test should be carried out according to the specified method (see above) before use. Because of the long interval between the use of benzathine penicillin, skin test should be carried out before each medication.
(2) The dosage should be adjusted or the interval of administration should be prolonged in patients with severe renal impairment.
(3) Intrathecal administration is not suitable.
(4) The aqueous solution of penicillin sodium salt or potassium salt is unstable, so it should be prepared and used now. When it must be kept, it should be put in the refrigerator to use it up on the same day.
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