What Is Cefalexin?

Cefalexin (Cefalexin), antibiotics \ -lactams \ cephalosporins. It can inhibit the synthesis of cell walls, swell cell contents to rupture and dissolve, and kill bacteria.

Chinese name: Cefalexin
English name: Cephalexin
nickname: Phenylcephalosporin; Cefosin etc.

Chemical formula: C16H17N3O4S
Molecular weight: 347.39
CAS Registry Number: 15686-71-2
EINECS registration number: 239-773-6

Cefalexin compounds

Cefalexin Basic Information

Chinese name: cephalosporin

Chinese alias: Cefalexin (monohydrate), Cefalexin monohydrate, Cefalexin monohydrate, Cephalosporin IV, Pioneeromycin IV, Cefalexin, Phenylpyramycin, Citalin, Cefalexin, (6R, 7R) -3-methyl-7-[(R) -2-amino-2-phenylacetamino] -8-oxo-5-thia-1-azabicyclo [4.2.0] octyl -2-ene-2-carboxylic acid-hydrate

English name: cephalexin monohydrate

English alias: Cephalexin monohydrate; Cefalexin (compacted); CEPHALEXIN MONOHYDRATE;

CAS number: 23325-78-2

Molecular formula: C ₁₆ H ₁₉ N ₃ O ₅ S

Molecular weight: 365.40400

Exact mass: 365.10500

PSA: 147.26000

LogP: 1.40970

Cefalexin Properties

Appearance and properties: white crystalline solid with bitter taste and slight odor. The product is slightly soluble in water and insoluble in ethanol, chloroform or ether.

Density: 1.5g / cm ³

Boiling point: 727.4ºC at 760 mmHg

Flash point: 393.7ºC

Storage conditions: 2-8ºC

Vapor pressure: 3.27E-22mmHg at 25 ° C

Cefalexin Safety Information

Danger category code: R42 / 43

Safety instructions: S22; S36 / 37; S45

Dangerous goods mark: Xn ^[1]

Cefalexin Safety Terms

S22Do not breathe dust.

Do not breathe dust.

S36 / 37Wear suitable protective clothing and gloves.

Wear suitable protective clothing and gloves.

S45In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)

In case of accident or if you feel unwell, seek medical advice immediately (show the label if possible).

Cefalexin risk term

R42 / 43May cause sensitization by inhalation and skin contact.

May cause sensitization by inhalation and skin contact.

Cephalexin Pharmacopoeia Standard

Cefalexin source (name), content (potency)

This product is (6R, 7R) -3-methyl-7-[(R) -2-amino-2-phenylacetamino] -8-oxo-5-thia-1-azabicyclo [4.2. 0] Oct-2-ene-2-carboxylic acid-hydrate. Calculated as anhydrous content, containing C16H17N3O4S shall not be less than 95.0%.

Cefalexin traits

This product is white to slightly yellow crystalline powder; slightly smelly.

This product is slightly soluble in water and insoluble in ethanol, chloroform or ether.

1 specific rotation

Take this product, weigh it accurately, dissolve it with water and quantitatively dilute it to make a solution containing about 5mg per 1ml, and measure it according to law (Appendix VIE of Part Two of the Pharmacopoeia, 2010 Edition). The specific rotation is + 149 ° to + 158 °.

2 absorption coefficient

Take this product, weigh it accurately, add water to dissolve and quantitatively dilute it to make a solution containing about 20 g per 1 ml. According to the UV-visible spectrophotometry (Appendix IVA of the Pharmacopoeia Part II of the 2010 edition), measure the absorbance at 262nm and absorb The coefficient () is 220 ~ 245.

Cefalexin identification

(1) In the chromatogram recorded under the content determination item, the retention time of the main peak of the test solution should be consistent with the retention time of the main peak of the reference solution.

(2) The infrared light absorption spectrum of this product should be consistent with the control spectrum ("Infrared Spectra of Drugs" 1090).

Cefalexin examination

acidity

Take 50mg of this product, add 10ml of water to dissolve it, and determine it according to law (Appendix VI H of the second edition of the Pharmacopoeia 2010), the pH value should be 3.5 5.5.

relative substance

Accurately weigh the appropriate amount of this product, add mobile phase A to dissolve and dilute it to make a solution containing about 1.0mg per 1ml. As a test solution, take 1ml precisely, place it in a 100ml volumetric flask, and dilute to the mark with mobile phase A. , Shake well, as a control solution; take about 7mg of 7-aminodesacetoxycephalosporanic acid reference substance and -phenylglycine reference substance, accurately weigh, put in the same 100ml measuring bottle, add pH 7.0 phosphate buffer solution Dissolve about 20ml by sonication, then dilute to the mark with mobile phase A and shake well. Precisely measure 2.0ml, place it in a 20ml volumetric flask, dilute to the mark with mobile phase A, shake well, and use it as the impurity reference solution. As determined by high performance liquid chromatography (Appendix VD of Part Two of the Pharmacopoeia, 2010 edition), octadecylsilane bonded silica gel was used as the filler; mobile phase A was a 0.2mol / L sodium dihydrogen phosphate solution (using sodium hydroxide test solution). Adjust the pH value to 5.0), the mobile phase B is methanol, and perform a linear gradient elution according to the following table; the detection wavelength is 220nm, take 20l of the impurity reference solution into the liquid chromatograph, record the chromatogram, 7-aminodeacetoxy The resolution of the cephalosporanic acid peak and the -phenylglycine peak should meet the requirements; take an appropriate amount of the test solution, heat it in a water bath at 80 ° C for 60 minutes, cool down, and take 20 l into the liquid chromatograph, record the chromatogram, and the cephalexin peak Resolution from adjacent impurity peaks should meet requirements. Take 20 l of the control solution and inject it into the liquid chromatograph to adjust the detection sensitivity so that the peak height of the main component chromatographic peak is about 25% of the full scale. Precisely measure 20 l each of the test solution, the control solution and the impurity reference solution, and inject them into the liquid chromatograph respectively. If there is an impurity peak in the chromatogram of the test solution, the The cr phenylglycine peak is calculated based on the external standard and the peak area, and all must not exceed 1.0%; the peak area of other individual impurities must not be greater than 1.5 times (1.5%) the main peak area of the control solution, and the sum of the peak areas of other impurities must not be greater than the main peak of the control solution. 2.5 times the area (2.5%). Any peaks smaller than 0.05 times the area of the main peak of the control solution in the chromatogram of the test solution can be ignored.

Time (minutes)	Mobile phase A (%)	Mobile phase B (%)
0	98	2
1	98	2
20	70	30
twenty three	98	2
30	98	2

2-naphthol

Determination according to high performance liquid chromatography (Annex VD of Pharmacopoeia Part II of the 2010 edition).

1 Chromatographic conditions and system suitability tests

Octadecylsilane-bonded silica gel was used as the filler; methanol monowater (55:45) was used as the mobile phase, the flow rate was 1 ml per minute, and the detection wavelength was 225 nm. Measure 20ul of the reference solution and inject it into the liquid chromatograph. Adjust the methanol ratio in the mobile phase so that the retention time of the 2-naphthol peak is about 7 minutes. The resolution of phenolic peaks and adjacent peaks should not be less than 1.5.

2 Assay

Take an appropriate amount of this product, accurately weigh it, add mobile phase quantitative dilution to make a solution containing about 10mg of cephalexin per 1ml, shake it thoroughly, take an appropriate amount of suspension, centrifuge at 15000 rpm for 5 minutes, and take the supernatant As a test solution; take an appropriate amount of 2-naphthol reference substance, accurately weigh it, add mobile phase to dissolve and quantitatively dilute it to make a solution containing about 0.5ug of 2-naphthol per Iml, and use it as a reference solution. Take 20ul of each of the above two solutions and inject them into the liquid chromatograph respectively to record the chromatogram. Based on the peak area calculated by the external standard method, the amount of 2-naphthol should not exceed 0.05%.

Moisture

Take this product and measure it according to the moisture determination method (Appendix M, the first method A of the second edition of the Pharmacopoeia, 2010 edition). The moisture content should be 4.0% to 8.0%.

Residue on ignition

Must not exceed 0.2% (Appendix N of Part Two of the 2010 Pharmacopoeia).

Determination of cephalexin

It was determined by high performance liquid chromatography (Appendix D, Part Two of the Pharmacopoeia, 2010 Edition).

Chromatographic conditions and system suitability tests

Use octadecylsilane bonded silica as filler; water-methanol-3.86% sodium acetate solution-4% acetic acid solution (742: 240: 15: 3) as mobile phase; detection wavelength is 254nm; take test sample An appropriate amount of solution is heated in a 80 ° C water bath for 60 minutes, cooled, and 20 l is injected into the liquid chromatograph, and the chromatogram is recorded. The resolution of the cephalexin peak and adjacent impurity peaks should meet the requirements.

Assay

Take about 50mg of this product, weigh it accurately, place it in a 50ml measuring bottle, add the mobile phase to dissolve and dilute to the mark, and shake well. Take a precise amount of 10ml, place it in a 50ml measuring bottle, and dilute to the mark with the mobile phase. Measure 10l into the liquid chromatograph and record the chromatogram. Another appropriate amount of cephalexin reference substance was measured in the same way. Calculate the peak area according to the external standard method.

Cephalexin categories

-lactam antibiotics, cephalosporins.

Cefalexin storage

Shaded, sealed and stored in a cool and dark place.

Cephalexin

(1) Cephalexin dry suspension (2) Cephalexin tablets (3) Cephalexin capsules (4) Cephalexin granules ^[2-3]

Cefalexin Drug Description

Cefalexin pharmacological effects

Cephalexin Cephalexin is a semi-synthetic first-generation oral cephalosporin. Its mechanism of action is by combining with one or more penicillin-binding proteins (PBPs) of bacteria (cephalexin mainly binds to PBP-3), and inhibiting the cell wall synthesis of bacterial dividing cells, thereby playing an antibacterial role. The antibacterial spectrum of cephalexin is similar to that of cephalosporin, but its antibacterial activity is worse than the latter. Except for Enterococcus and methicillin-resistant Staphylococci, Gram-positive cocci are sensitive to cephalexin. Cephalexin has a good antibacterial effect on Neisseria and a poor sensitivity to influenza bacillus. It has a certain antibacterial effect on some E. coli, Proteus mirabilis, Klebsiella pneumoniae, and Salmonella. Other Enterobacteria bacteria , Acinetobacter and Pseudomonas aeruginosa and B. fragile are resistant to cephalexin.

Cephalexin pharmacokinetics

The product is well absorbed, and the peak drug concentration (Cmax) is reached within 1 hour after oral administration of the product on an empty stomach.

Cefalexin capsules , The average is 18mg / L. Medication after meals prolongs absorption and reduces peak blood drug concentration, but absorption does not decrease. The absorption of this product can be increased in children with celiac disease and small intestinal diverticulum, and can be delayed and decreased in patients with Crohn's disease and pulmonary cystic fibrosis. Although the gastrointestinal absorption of the elderly did not decrease, the blood drug concentration remained longer than that of the younger. The blood elimination half-life (t1 / 2b) of this product is 0.6 to 1.0 hours. Adding probenecid can increase blood concentration, t1 / 2b can be extended to 1.8 hours; t1 / 2b can be extended to 5 to 30 hours in renal failure; The neonatal t1 / 2b was 6.3 hours. The product is widely distributed in various body fluids after absorption. The average concentration in sputum after oral administration of 0.5 g every 6 hours is 0.32 mg / L, and the concentration in purulent sputum is higher. The pus drug concentration and blood drug concentration are basically equal, and the drug concentration in joint exudate

Cefalexin granules It is 50% of the blood concentration.

The product can enter the fetal blood circulation through the placenta, and the maternal amniotic fluid; the milk concentration of the baby after oral administration of 0.5g is 5mg / L. About 5% of the oral dose is excreted from the bile, and the drug concentration in the bile is 1 to 4 times the blood concentration. The serum protein binding rate was 10% to 15%. The product is not metabolized in the body, and 80% to 90% of the cumulative dose excreted in the urine within 24 hours. The peak urine concentration after oral administration of 0.5g can reach 2.2g / L. Cefalexin is cleared by hemodialysis and peritoneal dialysis.

This product is the semi-synthetic first-generation oral cephalosporin. Its antibacterial spectrum is basically the same as that of cefotaxime and cefotaxime. Its antibacterial effect is weaker than the two. Good antibacterial effect on drug-resistant Staphylococcus aureus.

Mainly used for respiratory infections caused by sensitive bacteria, urinary tract infections, gynecological and obstetric infections, skin and soft tissue infections, and gonorrhea.

Cephalexin indications

Broad-spectrum antibiotics. Mainly used for Gram-positive and negative bacteria infections, such as: influenza, hemorrhagic septicemia, streptococcal disease, swine erysipelas, anthrax, emphysema, malignant edema, actinomycosis, necrotic disease, leptospirosis Septic hyperthermia (41-43 ° C) or persistently low temperature (less than 37 ° C) caused by treponemasis, etc., indigestion, drinking cold water, apathetic drowsiness, walking crutches, blue ears, tears, etc. It is also used to treat various inflammatory diseases, such as: infectious pleural pneumonia, pneumonia pneumonia, atrophic rhinitis, blue ear disease, mastitis, hysteritis, stomatitis, urethritis, etc. caused by cough, asthma, dyspnea, and low pregnancy , More stillbirths or piglets die 7-10 days after birth, breast swelling, milk deterioration, milk production decline, foot and mouth ulceration, salivation, sore and purulent.

Cephalexin dosage

Adult dosage: oral. Generally, 0.25 to 0.5 g (1 to 2 capsules) at a time, 4 times a day, the highest dose is 4 g (16 capsules) per day. Patients with impaired renal function should be dosed according to the degree of impaired renal function. Patients with simple cystitis, skin and soft tissue infection, and streptococcal angina are 0.5 g (4 capsules) every 12 hours.

Child dose: oral. According to the daily weight of 25-50mg / kg, 4 times a day. Patients with skin and soft tissue infections and streptococcal angina will take 12.5-50 mg / kg orally every 12 hours.

Cefalexin adverse reactions

1. Rash, urticaria, erythema, drug fever and other allergic reactions are more common, with occasional anaphylactic shock.

2. Gastrointestinal reactions: nausea, vomiting, diarrhea, and abdominal discomfort are more common, and occasionally pseudomembranous enteritis.

3. Nervous system response: A small number of patients may experience neurological reactions such as dizziness, diplopia, tinnitus, and convulsions.

4. Hepatotoxicity: A few patients may have transient liver dysfunction after administration (serum alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase transiently increase).

5. Renal toxicity: A small number of patients may have temporary elevated urea nitrogen, creatine, and creatinine after administration, and occasionally proteinuria and oliguria.

6. Blood system: Occasionally hemoglobin decreases, thrombocytopenia, neutropenia, and eosinophilia increase after medication.

7. Others: Long-term medication can cause bacterial flora imbalance and cause double infection; vitamin K and vitamin B deficiency can also occur.

Cefalexin contraindications

Those who are allergic to cephalosporins and those who have a history of anaphylactic shock or immediate reactions to penicillin are contraindicated.

Cefalexin precautions

Cephalosporins 1. Before applying this product, the patient must be asked in detail about the history of allergies to cephalosporins, penicillins and other drugs. People with a history of penicillin anaphylactic shock should not use this product. Other patients must pay attention to cephalosporin when applying this product The chance of cross-allergic reactions between penicillin and penicillin is about 5% to 7%, and it should be used with caution under close observation. In the event of an allergic reaction, the drug is discontinued immediately. If anaphylactic shock occurs, rescue must be carried out immediately, including measures to keep the airway open, inhale oxygen and use of adrenaline and glucocorticoids.

2. Patients with a history of gastrointestinal diseases, especially those with ulcerative colitis, localized enteritis or antibacterial drug-associated colitis (cephalosporin rarely produces pseudomembrane enteritis) and those with impaired renal function should be used with caution. Product.

3. Interference in diagnosis: direct Coombs test positive results and false urine glucose positive results (copper sulfate method) may occur when using this product; alkaline phosphatase, serum alanine aminotransferase and aspartate in a few patients Aminotransferases can be elevated.

4. When the daily oral dose exceeds 4g (anhydrocephalosporin), consider using cephalosporins for injection.

5. Cefalexin is mainly excreted by the kidney, and it should be reduced in patients with impaired renal function.

6. This product passes through the placenta, so pregnant women should use it with caution; this product can also be excreted through milk. Although there have been no reports of problems with cephalosporins in lactating women, it has to be weighed before using it.

Cefalexin drug interactions

1. Used with probenecid to delay the renal excretion of cefalexin and increase the blood concentration of cefalexin. However, probenecid has also been reported to increase the excretion of cefalexin in the bile.

2. Used with cholestyramine (cholestyramine) can reduce the average blood peak concentration of cephalexin.

3. The same use with aminoglycosides can increase renal toxicity.

4. Co-use with live typhoid vaccine may reduce the immune effect of live typhoid vaccine. The possible mechanism is that cephalexin has antibacterial activity against Salmonella typhi.

Cephalexin poisoning

Cephalexin (pionein IV, cefotaxime) is a broad-spectrum semi-synthetic antibiotic and belongs to the first generation of cephalosporins. It is mainly used to treat mild infections of the respiratory tract, urinary tract, skin and soft tissue caused by penicillinase-sensitive bacteria. The incidence of allergic reactions to penicillin allergy to this drug is about 1.1%. Topical application is highly irritating and less injection. The plasma protein binding rate of the drug is 10% to 15%, the half-life of normal adults is 0.6 to 1.0 hours, and that of newborns is 6.3 hours. For oral administration, the usual amount for adults is 0.25-0.5g, 4 / d; the highest amount is 4g / d.

Clinical manifestation

1. Gastrointestinal reactions are the most common, with an incidence of about 4.5%. They include diarrhea, nausea, vomiting, stomach pain, lack of appetite, and constipation. Individual serum transaminase increases. Rare headaches, dizziness, confusion, and general weakness.

2. Allergic manifestations include urticaria, maculopapular rash, general pruritus, drug fever, and eosinophilia. There are reports of positive Coomb's test.

3. The secondary infection mainly occurs in the perineum. Candida albicans or other drug-resistant bacteria are common.

4. Cefalexin has been reported to cause disulfide quitting in 2 cases. The patient drank beer after taking the drug for a few days and suffered general discomfort, chest tightness, shortness of breath, sweating, irritability, etc. ECG showed pre-atrial contraction, and after symptomatic treatment restore. Drinking beer the next day, the symptoms mentioned above appeared again. Disulfiram-like reactions caused by drinking liquor are more severe and even fatal. Many drugs such as cephalosporin antibiotics and panterin have their reactions, which should be paid attention to clinically.

5. There are reports of reversible gross hematuria and reversible acute renal failure and toxic psychosis.

treatment

The main points of treatment for cephalexin poisoning are:

1. Taking this medicine for people with impaired renal function can cause the half-life of this medicine to be prolonged in the body and aggravate kidney damage. Long-term and large-scale administration should be avoided.

2. When an allergic reaction occurs, the drug should be stopped immediately and anti-allergic treatment should be given.

3. When a double infection occurs, treat it according to the pathogenic microorganism.

4. Hemodialysis and hemoperfusion can effectively remove the drug from the body ^[4] .

Cefalexin expert review

Cefalexin has high concentrations in urine and pus, and is especially suitable for urogenital infections. It is effective for bacteremia, bacterial endocarditis, and meningitis, and for acute palate tonsillitis, sore throat, pneumonia, and bronchitis. , Lobar pneumonia and streptococcus-induced soft tissue infections are more effective ^[3] .