Oxacillin, 500 mg

Oxacillin is a bactericidal antibiotic from the group of semi-synthetic penicillins, resistant to the action of penicillinase. It blocks synthesis of the bacterial cell wall by disrupting the late stages of peptidoglycan synthesis (prevents formation of peptide bonds by inhibiting transpeptidase), causes lysis of dividing bacterial cells.

Active against Gram-positive microorganisms: Staphylococcus spp. (including those producing penicillinase), Streptococcus spp, including Streptococcus pneumoniae, Corynebacterium diphtheriae, Bacillus anthracis, anaerobic spore-forming bacilli, Gram-negative cocci (Neisseria gonorrhoeae, Neisseria meningitidis), Actinomyces spp.

It is inactive against most gram-negative bacteria, rickettsia, viruses, protozoa, fungi. Resistance develops slowly.

Pharmacokinetics

Absorption is fast and complete. It is stable in a slightly acidic environment. The binding to plasma proteins is about 90%. T_1/2 – 30 min. Time to reach C_max after intravenous injection is 1-2 h, concentration decreases rapidly by 4 h. When parenteral administration, higher blood concentrations are achieved than when administered orally. It is found in pleural fluid at a concentration as high as 10%, in synovial and ascitic fluid at 50%, in bile at 5-8% relative to its concentration in blood serum. It does not penetrate through the intact BBB, while in case of inflammation of the cerebral membranes penetration increases. It penetrates through the placental barrier and is detected in breast milk. After intravenous administration more than 40% is quickly excreted by the kidneys, and 10% is excreted with the bile.

Indications

Infectious diseases caused by Gram-positive microorganisms producing and not producing penicillinase:

Active ingredient

Composition

Active ingredient:

Oxacillin (sodium salt form) 500 mg

How to take, the dosage

Adults and children over 6 years – 2-4 g per day.

In children under 3 months of age – 60-80 mg/kg/day, from 3 months to 2 years – 1 g/day, from 2 to 6 years – 2 g/day.

In newborns and premature infants – 20-40 mg/kg/day.

The frequency of administration is 4 times a day (every 4-6 hours). The duration of treatment is usually 7-10 days. In severe forms of the disease (sepsis, septic endocarditis) treatment may last for 2-3 weeks or more.

When preparing solutions for intravenous injections, 1.5 ml is added to the vial with 250 mg, with 500 mg – 3 ml of water for injections.

When preparing solutions intended for intravenous injection, 250 mg or 500 mg are dissolved in 5 ml of water for injection or 0.9% sodium chloride solution and injected slowly over 5-10 minutes.

For intravenous drip administration, oxacillin sodium salt is dissolved in 0.9% sodium chloride solution or in 5% dextrose solution to a concentration of 0.5-2 mg/ml and is administered for 1-2 hours at a rate of 60-100 drops/min.

Interaction

Increases methotrexate toxicity (competition for tubular secretion).

It may require increased doses of calcium folinate (antidote of folic acid antagonists) and longer use.

The combination of ampicillin or benzylpenicillin with oxacillin is rational because the latter, by inhibiting penicillinase activity, reduces the degradation of ampicillin and benzylpenicillin. The spectrum of action with this combination becomes wider.

The concomitant use with other drugs with hepatotoxic effects should be avoided.

It is not recommended to use simultaneously with bacteriostatic antibiotics (decrease in effectiveness).

Drugs that block tubular secretion increase the concentration of oxacillin in the blood.

The antacids and laxatives decrease absorption of the drug from the gastrointestinal tract.

Special Instructions

It is inadvisable for infections caused by microorganisms sensitive to benzylpenicillin.

Contraindications

Hypersensitivity, including to other beta-lactam antibiotics.

With caution: history of allergic reactions and/or bronchial asthma, chronic renal failure (CKD), enterocolitis on antibiotic use (history).

Side effects

Allergic reactions: skin itching, urticaria, rarely – angioedema, bronchospasm, in rare cases anaphylactic shock, eosinophilia.

Digestive system disorders: dyspepsia (nausea, vomiting, diarrhea); pseudomembranous enterocolitis, oral candidiasis; hepatotoxic effect – usually occurs when administered in dose more than 6 g/day (hyperthermia, nausea, vomiting, jaundice of sclerae or skin, increased liver transaminase activity).

Urogenital system disorders: hematuria, proteinuria, interstitial nephritis, vaginal candidiasis.

Pregnancy use

In pregnancy and lactation the drug is prescribed only for vital indications. Administration of the drug during pregnancy and lactation is possible only when the estimated benefit to the mother exceeds the potential risk to the fetus.

Oxacillin is excreted with breast milk, therefore if it is necessary to prescribe the drug during lactation period it is necessary to stop breast-feeding.