Understanding the Need for Alternatives: The Bicillin L-A Shortage
Bicillin L-A, the brand name for an injectable suspension of penicillin G benzathine, is a critical long-acting antibiotic manufactured by Pfizer [1.6.3, 1.6.6]. It is the first-line and often the only recommended treatment for serious bacterial infections like syphilis, particularly in pregnant individuals to prevent congenital syphilis [1.3.4]. Since April 2023, the United States has experienced a significant shortage of Bicillin L-A due to increased demand, largely driven by rising syphilis infection rates [1.6.6, 1.7.1]. This has created a public health challenge, prompting federal agencies to find viable alternatives.
In response, the U.S. Food and Drug Administration (FDA) has exercised its enforcement discretion to allow the temporary importation of Extencilline [1.7.3]. Extencilline is a brand name for benzathine benzylpenicillin, which is therapeutically equivalent to Bicillin L-A's active ingredient [1.3.6]. It is manufactured by Laboratories Delbert in Italy and is marketed in France [1.6.6, 1.8.6]. This measure aims to mitigate the effects of the Bicillin L-A shortage and ensure continuity of care for patients requiring this essential medication [1.7.3].
Core Component: Penicillin G Benzathine
The active ingredient in both Bicillin L-A and Extencilline is penicillin G benzathine (also known as benzathine benzylpenicillin) [1.4.2, 1.5.1]. This long-acting form of penicillin works by inhibiting the biosynthesis of the bacterial cell wall, rendering it unstable and leading to the death of susceptible microorganisms [1.4.5]. After a deep intramuscular injection, it is absorbed very slowly into the bloodstream, resulting in lower but much more prolonged serum levels compared to other parenteral penicillins [1.4.5]. This allows for less frequent dosing, often a single injection, for certain infections [1.4.3].
This antibiotic is effective against a range of penicillin-sensitive bacteria and is indicated for:
- Venereal Infections: Primarily syphilis, but also yaws, bejel, and pinta [1.4.1].
- Streptococcal Infections: Mild-to-moderate upper-respiratory tract infections like pharyngitis [1.4.7].
- Prophylaxis: Preventing recurrence of rheumatic fever and/or chorea [1.4.1].
Head-to-Head Comparison: Bicillin L-A vs. Extencilline
While clinically interchangeable for treating conditions like syphilis, there are several practical and formulation differences that healthcare providers must be aware of when substituting Extencilline for Bicillin L-A [1.2.1].
Formulation and Preparation
The most significant difference lies in their form and preparation:
- Bicillin L-A: Supplied in prefilled, disposable syringes containing an aqueous suspension of the drug. It is ready for immediate administration [1.3.2].
- Extencilline: Supplied as a powder in a vial that requires reconstitution before use. It comes with a separate ampule of diluent (sterile water for injection) [1.5.1]. Healthcare providers must aseptically mix the powder and diluent, shaking the vial for at least 20 seconds to create a homogenous suspension [1.5.1].
Injection Volume
After preparation, the resulting injection volume of Extencilline is substantially larger than that of Bicillin L-A for an equivalent dose:
- 1,200,000 unit dose: Bicillin L-A is 2 mL, whereas Extencilline is approximately 5 mL [1.2.2, 1.3.2].
- 2,400,000 unit dose: Bicillin L-A is 4 mL, whereas Extencilline is approximately 7 mL [1.2.2, 1.3.2].
This larger volume can be more painful for the patient and may require the dose to be split into two separate simultaneous injections in different sites (e.g., one in each buttock) [1.2.2]. To help manage injection pain, the reconstitution protocol allows for the use of 1% or 0.5% lidocaine instead of sterile water [1.5.1].
Excipients and Allergy Concerns
The inactive ingredients, or excipients, also differ. A key distinction is that Extencilline contains soy phospholipids [1.3.2]. This poses a risk of hypersensitivity reactions, including urticaria (hives) and anaphylactic shock, in patients with a known allergy to soybeans. Bicillin L-A's formulation does not list soy as an ingredient [1.3.1, 1.4.5].
Labeling and Warnings
As Extencilline is not an FDA-approved product, its labeling differs from the U.S. standard seen on Bicillin L-A packaging [1.3.3]. Healthcare providers are advised to refer to the Bicillin L-A prescribing information for complete warnings [1.3.2]. Notable differences in labeling include:
- Extencilline labeling does not feature the FDA's black box warning against intravenous use [1.2.5].
- The specific warning "Fatal if given by other routes" is not present on the Extencilline carton [1.2.3].
- Detailed instructions for deep intramuscular administration are not included on the Extencilline label [1.2.5].
| Feature | Bicillin L-A | Extencilline |
|---|---|---|
| Active Ingredient | Penicillin G Benzathine [1.4.1] | Benzathine Benzylpenicillin [1.5.1] |
| Form | Prefilled injectable suspension [1.3.2] | Powder for reconstitution [1.3.2] |
| Preparation | Ready to use [1.3.2] | Requires mixing powder with diluent [1.5.1] |
| Injection Volume (2.4M units) | 4 mL [1.3.2] | ~7 mL [1.3.2] |
| Soy Allergen | No | Contains soy phospholipids [1.3.1] |
| Storage (Unused) | Refrigerate (2° to 8°C) [1.4.5] | Room temperature (powder vial) [1.5.1] |
| Storage (Prepared) | N/A | Must be used immediately [1.5.1] |
| FDA Approval | Approved [1.7.2] | Not FDA-approved; temporarily imported [1.8.4] |
Conclusion
Bicillin L-A and Extencilline are therapeutically equivalent due to their shared active ingredient, penicillin G benzathine, making Extencilline a vital alternative during the ongoing Bicillin L-A shortage [1.3.6]. However, the difference between them is significant from a practical standpoint. Healthcare professionals must be diligent about the differences in preparation, the larger administration volume which may necessitate split doses, the potential for allergic reactions in patients with soy allergies, and the variations in product labeling and warnings [1.2.1, 1.3.2]. Careful adherence to the specific preparation and administration guidelines for Extencilline is crucial to ensure patient safety and therapeutic effectiveness.
For more detailed clinical guidance, healthcare providers can refer to resources provided by the CDC. https://www.cdc.gov/sti/hcp/clinical-guidance/availability-of-products.html
