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.
กลไกการออกฤทธิ์: Spectinomycin works by binding to the **30S ribosomal subunit** of susceptible bacteria. **Mechanism Pathway:** Drug enters bacterial cell → Binds specifically to the 30S ribosomal subunit → **Inhibits mRNA translation** and translocation → Halts protein synthesis → **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.*
ขนาดยาตามชนิดสัตว์
- For acute infectious gastroenteritis · 5-12 mg/kg · IM · q12h
- For bronchopneumonia and fibrinous pneumonia · 33 mg/kg · SC · q8h · Suggested withdrawal time is 60 days.
- For susceptible infections · 22-39.6 mg/kg/day · IM · divided three times daily
- For bovine respiratory disease · 10-15 mg/kg · SC · once daily (q24h) · for 3-5 consecutive days · Inject in the neck; not more than 50 mL per site.
- For susceptible infections · 20 mg/kg · IM · three times daily
- For pneumonia · 20 mg/kg · IM · q8h · 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) · 0.1 mL (10 mg) · SC · once · 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 · 2.55 mg/0.2 mL · SC · once · Dilute injection with normal saline to a concentration of 2.55 mg/0.2 mL and inject SC.
วิธีการให้ยา
ข้อห้ามใช้
- Patients with known hypersensitivity to spectinomycin
อาการไม่พึงประสงค์
- 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)
อันตรกิริยาระหว่างยา
- chloramphenicol · Antagonism has been reported when used concurrently.
- tetracycline · Antagonism has been reported when used concurrently.
การติดตาม
- Clinical efficacy (resolution of infection symptoms)
- Injection site monitoring for swelling or myositis
การได้รับยาเกินขนาด
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.
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