What are the side effects of nafcillin?

Posted on  March 7, 2021, Edited by Jason, Category  

What is Nafcillin?

1. Definition

Nafcillin is an oral and injectable penicillin that is chemically semi-synthesized for 6-aminopenicillin. It is white or yellowish white powder, slightly smelly, easily soluble in water, chloroform and ethanol. It is stable to acid and penicillinase. Clinically, it is mainly used for penicillin-resistant Staphylococcus infections and other penicillin-sensitive bacterial infections.

Its activity against drug-resistant Staphylococcus aureus is close to oxacillin, but stronger than methicillin. It is especially effective against hemolytic streptococcus and pneumococcus. It has incomplete oral absorption, low blood concentration and low urine excretion. The blood concentration of intramuscular injection is higher than that of oral administration, but it is still low. The concentration of traditional Chinese medicine in bile is higher than that of blood, and 90% is excreted by bile. The plasma protein binding rate is high (about 87%).

2. Formulation specifications

There are several dosage forms and specifications of nafcillin. Different manufacturers' preparations may have different drug effects and adverse reactions due to different manufacturing processes. Please consult your doctor for specific options.

  • Nafcillin sodium injection (powder): 1 g.
  • Nafcillin sodium capsules: 0.25 grams.

3. Pharmacology and Toxicology

This strain is acid-resistant and enzyme-resistant semi-synthetic penicillin. It is stable to acid and can be taken orally or parenterally. It is stable to penicillinase. Nafcillin is resistant to staphylococcus that produces penicillinase or is resistant to Penicillin g due to other reasons. It has special effects on hemolytic streptococcus, viridis streptococcus, and also has significant antibacterial and bactericidal effects on hemolytic cocci, viridis streptococcus and pneumococcus and other gram-positive bacteria.

The minimum inhibitory concentrations of nafcillin for Staphylococcus aureus which is sensitive and resistant to penicillin are 0.4 and 0.48ug/ml, respectively. The minimum inhibitory concentrations for pneumococcus, streptococcus viridis, meningococcus, and gonococcus are respectively 0.02, 0.4, 0.8 and 3.1ug/ml.

4. Pharmacokinetics

After intramuscular injection of 0.5 g of nafcillin, the serum concentration reached a peak of 7.93ug/ml after half an hour. After taking 1g of nafcillin for normal people, the blood concentration could reach the peak within 1 hour, about 14.34ug/ml. Oral probenecid can double the blood concentration. The serum half-life of nafcillin is more than 1.5 hours.

Nafcillin is widely distributed, and the effective drug concentration is concentrated in the gallbladder, kidney, lung, heart, intestine and liver; the highest concentration is in the small intestine, liver, and kidney;

After intramuscular injection of 1.5g of nafcillin, in the synovial fluid of the inflamed knee joint, the therapeutic concentration can be reached in the medium; the high concentration is maintained in the bile. Within 4 hours after intravenous injection, 93% of the dose appears in the bile. Nafcillin has a good reabsorption in the intestine.

Nafcillin is mainly excreted through bile and urine. After 6 hours of intramuscular injection and oral administration of Nafcillin, 14% and 7% of the dose were excreted in urine, 18-19% was excreted in urine on the third day, and urine on the eighth day 21% and 19.4% of the total amount excreted in the feces; regardless of oral or intramuscular injection, within 12 hours, 10% of the dose is excreted in the feces.

By the eighth day, the total amount excreted in the feces is about up to 50%, slow urinary excretion and long-term bile excretion may be the main reasons why nafcillin maintains a durable and effective bactericidal concentration. Nafcillin has a high serum protein binding rate, but has little effect on its antibacterial effect.

Nafcillin Uses


1. Indications

It is acid-resistant and enzyme-resistant semi-synthetic penicillin. It is stable to acid and can be administered orally or parenterally. It is also stable to penicillinase. Nafcillin has special effects on Staphylococcus resistant to penicillin g, hemolytic streptococcus and viridis streptococcus. It has significant antibacterial and bactericidal effects on Gram-positive bacteria such as hemolytic streptococcus, viridis streptococcus and pneumococcus.

Nafcillin is suitable for penicillin-resistant Staphylococcus infections and other penicillin-sensitive bacterial infections, such as: sepsis, bacteremia, endocarditis, empyema, liver abscess, pneumonia, osteomyelitis, meningitis, peritonitis, cellulitis, scarlet fever, tonsillitis, pharyngitis, otitis media, erysipelas, urinary tract infection, bronchitis, Tetanus, gas gangrene, anthrax, diphtheria, gonorrhea, gonococcal arthritis and ophthalmia.

2. Uses

Nafcillin is a semi-synthetic penicillin resistant to beta lactamase and acid. It is stable to penicillinase and has antibacterial and bactericidal effects. It is suitable for the treatment of staphylococcal infections resistant to penicillin and other bacterial infections sensitive to penicillin, such as sepsis, endocarditis, empyema, liver abscess, pneumonia, osteomyelitis, etc. It is mainly used as the preferred choice with an effective rate of over 85% for the treatment of drug-resistant Staphylococcus aureus infections.

In recent years, nosocomial infections caused by multi-drug resistant Staphylococcus aureus is not only a thorny problem that clinicians must often face, but also poses a great threat to the health of all human beings. Vancomycin, once known as the “final bottom line” of clinical anti-infection, has always been a preferred clinical treatment for gram-positive infections. However, vancomycin-resistant Staphylococcus aureus has been isolated in many countries, which is important for the development of new anti-infective treatments, therefore a necessitous request was asked·

Initially, the sensitivity of Staphylococcus aureus to penicillin was above 90%, so most of the antibiotics have played a good clinical role in the treatment of diseases caused by Staphylococcus aureus. However, with the extensive use of antibiotics, penicillin-resistant Staphylococcus aureus also appeared, and other antibiotic-resistant Staphylococcus aureus, such as tetracycline, erythromycin, etc., were also discovered. Therefore, for a long time, the treatment for resistant Staphylococcus aureus infections did not achieve the expected results. Microbial drug resistance mutations are the result of structural changes in a specific location of DNA molecules, and have nothing to do with the existence of drugs. The existence of a certain drug is only a means to isolate a certain drug-resistant strain.

Syphilis is a chronic infectious disease caused by Treponema pallidum, which is a sexually transmitted disease. In the initial stage, it is a systemic infection, which can invade any organs and tissues during the development process and cause various symptoms. Sometimes it can be latent for many years or even lifelong without any manifestations, and the course of the disease is slow.

The disease is mainly transmitted to others through sexual behavior, and it can also be transmitted to the next generation through the placenta. Because of the various manifestations of syphilis, most of which are complicated by bacterial infections. So antibiotics that treat both should be chosen. At present, it has been proved that nafcillin sodium which is broad-spectrum, safe, enzyme-resistant, and acid-resistant third-generation penicillin has specific effects on syphilis.

3. Dosage

  • Oral: 0.25~1g/time, 4-6 times/day, take it on an empty stomach.
  • Intramuscular or intravenous injection: 4-6/day, divided into 4 times, dissolved with water for injection or isotonic saline.
  • Local application: 0.2% to 1% aqueous solution can be used on wounds and ears.
  • Medication for pregnant women and lactating women: There is a lack of adequate research on the effect of nafcillin on pregnant women, so pregnant women should only use nafcillin when it is really necessary. A small amount of nafcillin can be secreted from breast milk, and breastfeeding women should stop breastfeeding when taking the drug.
  • Child medication: Newborns, especially premature infants, should use it with caution.

Nafcillin side effects


1. Adverse reactions

Oral administration can cause gastrointestinal reactions: nausea, vomiting, loss of appetite, abdominal distension, diarrhea. Those with penicillin allergies should not use it. Some cases have leukopenia, skin rash, drug fever, headache, and palpitations. Large doses may cause neurological reactions, such as confusion, convulsions, and convulsions. Children can have foreign taste in the mouth (such as metallic taste). Skin necrosis and local tissue damage may occur after intravenous injection. It can cause kidney damage, secondary interstitial nephritis, can cause liver damage.

  • Allergic reaction: It can cause anaphylactic shock or even death. Once it occurs, it must be rescued on the spot. Other allergic reactions include hemolytic anemia (type Ⅱ allergy), drug rash, contagious dermatitis, interstitial nephritis, asthma attacks and so on.
  • Intravenous nafcillin can cause rare agranulocytosis.
  • Very few patients have prolonged bleeding after giving nafcillin intravenously. Such adverse reactions may be caused by poor platelet function.
  • Interstitial nephritis.
  • Intravenous high-dose (≥12 grams per day) medication may cause hepatitis-like liver insufficiency or cholestasis after stopping the drug.
  • Occasionally, it can cause asymptomatic and persistent increase in serum AKP, AST, and ALT concentrations.
  • It can cause phlebitis or thrombophlebitis.
  • Nafcillin leaks outside the blood vessels and can cause severe chemical irritation to surrounding tissues, leading to tissue ulcers and necrosis.
  • Double infection: Penicillin-resistant Staphylococcus aureus, gram-negative bacilli or albicans Candida infection may occur during treatment. The overgrowth of Candida can make the tongue coating brown or even black.
  • Herxheimer reaction and treatment contradiction: seen in syphilis, leptospirosis or other infectious diseases.

2. Matters needing attention

Nafcillin is a prescription drug and must be prescribed by a doctor based on your condition. Self-administration may increase the risk: waste of drug resources, delay the illness, develop resistance, and serious adverse drug reactions.

According to the standards promulgated by the US Food and Drug Administration (FDA), nafcillin belongs to level B during pregnancy: studies on animal reproduction did not show a risk to the fetus, but no appropriate studies with control groups have been conducted in pregnant women.

  • Allergic reactions, nausea, vomiting, abdominal distension, elevated transaminase, renal function damage, etc.; intramuscular injection pain; intravenous injection can cause phlebitis. An allergy test is required before use.
  • Loss of appetite, bad taste in the mouth, nausea, bloating, etc.
  • Sometimes alanine aminotransferase can temporarily increase.
  • Do allergy test before use.
  • If anaphylactic shock occurs, the drug should be stopped immediately, and 0.5 to 1 mg of epinephrine should be injected subcutaneously or intramuscularly as soon as possible. Patients with cardiac arrest can be injected intracardiac; give oxygen at the same time, combined with antihistamines and corticosteroids.
  • If you use nafcillin again 48 hours later, you should do a skin test again; if you use a different batch of penicillins or different manufacturers of penicillins 24 hours after stopping the drug, you should also do a skin test.
  • If the skin test result is negative, hypersensitivity or allergic reactions may occur, so don’t be not careful.
  • Pay attention to prevent cross-allergic reactions. Patients who are allergic to one penicillin may be allergic to other penicillins, penicillamine or cephalosporins.
  • Penicillins can be excreted in small amounts through breast milk, and breastfeeding women should stop breastfeeding when taking the drug.
  • Nafcillin cannot be removed by hemodialysis.

3. Compatibility

  • Nafcillin is contraindicated with aminoglycosides, norepinephrine, meta-hydroxyamine, phenobarbital, vitamin B group, vitamin C and other drugs, so it is not suitable for infusion in the same bottle.
  • Probenecid can reduce the renal tubular secretion of naphthacillin and prolong the serum half-life of nafcillin.
  1. Probenecid can reduce the renal tubular secretion of naphthacillin and prolong the serum half-life of nafcillin.
  2. Ascilin and sulfa drugs reduce the absorption of nafcillin in the gastrointestinal tract, and can inhibit the binding of nafcillin and serum proteins, and increase the free blood concentration of nafcillin.


Nafcillin, a semi-synthetic penicillin, has a special effect on Staphylococcus which is resistant to Penicillium g. Its anti-resistant Staphylococcus aureus activity is close to oxacillin.

Nafcillin belongs to beta lactams. BALLYA provides a betalactam test to tell you if there are beta lactams residues in dairy products you eat every day.


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