What is the Trade Name for Quinupristin?
The trade name for the antibiotic quinupristin is Synercid. It is important to note that Synercid is not a single drug but a combination product containing two semi-synthetic streptogramin derivatives: quinupristin and dalfopristin. This combination is formulated for intravenous (IV) administration and is a critical, though now less commonly used, treatment for specific, severe bacterial infections.
The Components and Their Synergistic Action
The name Synercid is derived from the synergistic action of its two components, quinupristin and dalfopristin. Individually, these agents are typically only bacteriostatic (they stop bacterial growth), but when used together, they achieve a potent bactericidal effect (they kill bacteria) against sensitive organisms.
- Dalfopristin: This component binds to the 23S portion of the 50S ribosomal subunit in bacteria. This binding action changes the shape of the ribosome, which dramatically increases the binding efficiency of quinupristin.
- Quinupristin: Binding to a site on the 50S ribosomal subunit near dalfopristin, quinupristin then prevents the elongation of the polypeptide chain, disrupting protein synthesis entirely.
This two-pronged attack makes the combination highly effective against certain drug-resistant pathogens.
Clinical Uses of Synercid
Synercid is a reserve antibiotic, meaning its use is restricted to serious infections where other therapies have failed. Its primary approved uses include:
- Vancomycin-Resistant Enterococcus faecium (VRE) Infections: Synercid is indicated for severe or life-threatening infections caused by VRE bacteremia. It is crucial to note that it is not effective against Enterococcus faecalis, as most isolates are inherently resistant.
- Complicated Skin and Skin Structure Infections (cSSSI): Synercid is also approved for treating complicated skin infections caused by certain susceptible bacteria, such as methicillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus pyogenes.
Important Considerations and Side Effects
Despite its effectiveness against certain resistant pathogens, the use of Synercid has been limited over time due to its side effect profile and the emergence of newer, often better-tolerated alternatives, such as linezolid. Clinicians must weigh the benefits against the risks for each patient.
Commonly reported side effects include:
- Infusion Site Reactions: Pain, inflammation, edema, and thrombophlebitis at the IV infusion site are frequently observed. Proper administration and potentially a central line are often necessary.
- Musculoskeletal Pain: Myalgia (muscle aches) and arthralgia (joint pain) can occur, sometimes severe enough to warrant discontinuation of treatment.
- Gastrointestinal Distress: Nausea, diarrhea, and vomiting are also possible side effects.
- Allergic Reactions: Rare but severe allergic reactions, including anaphylaxis, have been reported.
Significant Drug Interactions
A major drawback to Synercid's use is its potent inhibition of the cytochrome P450-3A4 (CYP3A4) enzyme system in the liver. This can lead to clinically significant interactions by increasing the plasma concentrations of many other drugs metabolized by this pathway, such as:
- Statins: Atorvastatin, lovastatin, and simvastatin.
- Immunosuppressants: Cyclosporine and tacrolimus.
- Calcium Channel Blockers: Nifedipine and diltiazem.
- Anti-arrhythmics: Quinidine.
Clinicians must carefully review all current medications before prescribing Synercid and monitor patients closely for potential drug toxicities.
Synercid vs. Other Antibiotics for Resistant Gram-Positive Infections
| Feature | Synercid (Quinupristin/Dalfopristin) | Linezolid | Vancomycin |
|---|---|---|---|
| Drug Class | Streptogramin | Oxazolidinone | Glycopeptide |
| Mechanism | Inhibits protein synthesis at the 50S ribosomal subunit | Inhibits protein synthesis at the 50S ribosomal subunit | Inhibits cell wall synthesis |
| Targeted Pathogens | VRE (E. faecium only), MSSA, S. pyogenes | VRE (E. faecium and E. faecalis), MRSA, and other Gram-positive pathogens | MRSA, Streptococcus spp., C. difficile (oral) |
| Side Effects | Infusion site pain, myalgia, arthralgia, GI issues, CYP3A4 inhibition | Myelosuppression (long-term), peripheral neuropathy, optic neuropathy | Ototoxicity, nephrotoxicity (requires monitoring) |
| Administration | IV only | IV and oral | IV only (except oral for C. difficile) |
| Current Usage | Relatively rare due to side effects and newer options | Common for resistant Gram-positive infections | Very common, but resistance is a growing concern |
Conclusion
Synercid is the trade name for the combination antibiotic quinupristin/dalfopristin, an intravenous drug primarily used for serious infections involving vancomycin-resistant Enterococcus faecium and complicated skin infections. Its unique synergistic mechanism of action makes it effective against specific resistant bacteria. However, its limited spectrum of activity, notable side effect profile—especially infusion-related issues and musculoskeletal pain—and significant drug interactions via CYP3A4 inhibition have limited its clinical use over time, leading to it being largely replaced by newer antibiotics like linezolid. Despite this, Synercid remains a valuable tool in the infectious disease pharmacopoeia for specific, challenging cases. For more comprehensive information, consult authoritative sources such as the American Academy of Family Physicians, which has published detailed articles on this medication.
