Pharmacological Class and Classification
Azlocillin (Azlocillin) belongs to the broad group of beta-lactam antibiotics. Within this group, it represents the broad-spectrum semi-synthetic penicillins, specifically the ureidopenicillin subclass.
Its closest pharmacological relatives within this subclass are piperacillin and mezlocillin. Historically and pharmacologically, ureidopenicillins are compared with another subclass—the carboxypenicillins (carbenicillin, carfecillin, ticarcillin)—since both groups were developed to target severe Gram-negative infections.
Spectrum of Antimicrobial Activity
The baseline activity spectrum of azlocillin is similar to that of carboxypenicillins, but it offers two critical advantages:
- Expanded Spectrum: Azlocillin demonstrates higher activity against Klebsiella species and more effectively suppresses Gram-positive flora.
- Anti-Pseudomonal Potency: This is the primary indication for the drug. Azlocillin is 4–8 times more active against Pseudomonas aeruginosa than carboxypenicillins.
Comparative Anti-Pseudomonal Activity
Ranking semi-synthetic penicillins by descending efficacy against Pseudomonas infections (from most to least active):
- Rank 1 (Highest activity): Azlocillin and Piperacillin.
- Rank 2 (Moderate activity): Mezlocillin and Ticarcillin.
- Rank 3 (Lowest activity in the series): Carbenicillin.
Resistance Profile
Despite its high antibacterial potency, azlocillin has a significant vulnerability. The drug is hydrolyzed by $\beta$-lactamases—specific enzymes produced by staphylococci and many Gram-negative bacteria.
This means that for infections caused by $\beta$-lactamase-producing strains, azlocillin monotherapy will be ineffective: bacteria simply cleave the beta-lactam ring of the antibiotic before it can exert its bactericidal effect.
Formulations and Administration
Azlocillin is not absorbed from the gastrointestinal tract, so it is administered parenterally only. The drug is supplied as a powder in vials, from which a solution is prepared ex tempore (immediately prior to use).
Vial dosages depend on the route of administration:
- For intramuscular (IM) injection: 0.5 g, 1.0 g, and 2.0 g vials.
- For intravenous (IV) injection: Larger volume vials—4.0 g, 5.0 g, and 10.0 g.
Standard Regimen: The drug is administered intramuscularly or intravenously (bolus or infusion). A 10% aqueous solution is prepared for this purpose. The standard adult dose is 2.0 g 4 times daily.
Prescription Example
Prescribing azlocillin for intramuscular administration according to the standard regimen (2.0 g 4 times daily) for 5 days. For one day, 4 vials of 2.0 g are required; for a 5-day course, 20 vials.
```latin Rp.: Azlocillini 2,0 D.t.d. N. 20 S. Intramuscularly. Dissolve the vial contents in water for injection (to yield a 10% solution), administer 2.0 g 4 times daily. ```