Spectinomycin
Spectinomycin is an **aminocyclitol antibiotic**, structurally related to aminoglycosides but lacking the amino sugars and glycosidic bonds. **Clinical Pearls:** * **Bacteriostatic vs. Bactericidal:** Because of its structural differences from true aminoglycosides, spectinomycin is **bacteriostatic** rather than bactericidal. * **Safety Profile:** It notably lacks the severe nephrotoxicity and ototoxicity commonly associated with traditional aminoglycosides (like gentamicin or amikacin). * **Spectrum of Activity:** It has a relatively broad spectrum against many gram-positive and gram-negative bacteria (including *E. coli*, *Klebsiella*, *Proteus*, *Enterobacter*, *Salmonella*, *Streptococci*, *Staphylococcus*, and *Mycoplasma*). * **Limitations:** It has minimal to no activity against anaerobes, most strains of *Pseudomonas*, *Chlamydia*, or *Treponema*. * **Primary Use:** It is predominantly used in food-producing animals (swine, poultry, cattle) for respiratory and enteric infections, though it is occasionally used off-label in dogs, cats, and horses.
Mechanism: Spectinomycin works by binding to the **30S ribosomal subunit** of susceptible bacteria. **Mechanism Pathway:** Drug enters bacterial cell โ Binds specifically to the 30S ribosomal subunit โ **Inhibits mRNA translation** and translocation โ Halts protein synthesis โ **Bacteriostatic effect** (prevents bacterial replication and growth). *Note: Unlike true aminoglycosides, spectinomycin does not cause misreading of the messenger RNA, which explains why its action is bacteriostatic rather than bactericidal.*
Dosing by species
- For acute infectious gastroenteritis ยท 5-12 mg/kg ยท IM ยท q12h
- For bronchopneumonia and fibrinous pneumonia ยท 33 mg/kg ยท SC ยท q8h ยท Suggested withdrawal time is 60 days.
- For susceptible infections ยท 22-39.6 mg/kg/day ยท IM ยท divided three times daily
- For bovine respiratory disease ยท 10-15 mg/kg ยท SC ยท once daily (q24h) ยท for 3-5 consecutive days ยท Inject in the neck; not more than 50 mL per site.
- For susceptible infections ยท 20 mg/kg ยท IM ยท three times daily
- For pneumonia ยท 20 mg/kg ยท IM ยท q8h ยท May cause local myositis. Insufficient data to comment on use.
- For airsacculitis associated with M. meleagridis or chronic respiratory disease associated with E. coli in turkey poults (1-3 days old) ยท 0.1 mL (10 mg) ยท SC ยท once ยท Inject in the base of the neck.
- For control and to lessen mortality due to infections from M. synoviae, S. typhimurium, S. infantis, and E. coli in newly hatched chicks ยท 2.55 mg/0.2 mL ยท SC ยท once ยท Dilute injection with normal saline to a concentration of 2.55 mg/0.2 mL and inject SC.
Routes of administration
Contraindications
- Patients with known hypersensitivity to spectinomycin
Adverse effects
- Neuromuscular blockade (reversible with parenteral calcium)
- Swelling or soreness at injection sites (especially SC in cattle)
- Transient ataxia (reported in turkey poults at high injected doses)
- Mild increases in BUN, ALP, and SGPT (reported in humans)
- Decreases in hemoglobin, hematocrit, and creatinine clearance (reported in humans)
Drug interactions
- chloramphenicol ยท Antagonism has been reported when used concurrently.
- tetracycline ยท Antagonism has been reported when used concurrently.
Monitoring
- Clinical efficacy (resolution of infection symptoms)
- Injection site monitoring for swelling or myositis
Overdose
Because the drug is negligibly absorbed after oral administration, **significant systemic toxicity is highly unlikely via the oral route**. Injected overdoses may cause neurological or neuromuscular signs. For example, injected doses of 90 mg produced transient ataxia in turkey poults. If severe neuromuscular blockade occurs following massive parenteral overdose, parenteral calcium administration may be required to reverse the blockade.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.