米諾環素
米諾環素是一種高脂溶性的第二代**四環黴素類抗生素**。它以優異的組織穿透力著稱，能穿透血腦屏障並進入前列腺。 - **臨床用途：** 布氏桿菌症、萊姆病、血液黴漿菌症、非典型分枝桿菌感染及具抗藥性的院內感染。 - **優點：** 與早期水溶性較高的四環黴素相比，較不易引起骨骼和牙齒異常。可用於中度腎功能不全的病患，無需調整劑量。 - **其他特性：** 除了抗菌效果外，米諾環素還具有**抗發炎**和**神經保護**特性（例如抑制基質金屬蛋白酶），因此被研究作為血管肉瘤等疾病的輔助療法，儘管早期結果不如預期。
作用機制: Minocycline is a **bacteriostatic** antibiotic that exhibits time-dependent (AUC/MIC) inhibition of bacterial growth. - **Primary Mechanism:** Reversibly binds to the **30S ribosomal subunit** of susceptible organisms → blocks the binding of aminoacyl transfer-RNA to the mRNA-ribosome complex → **inhibits bacterial protein synthesis**. - **Secondary Mechanism:** Reversibly binds to the **50S ribosomal subunit** → alters cytoplasmic membrane permeability, leading to leakage of intracellular components. - **Mammalian Effects:** At very high concentrations, it can inhibit mammalian protein synthesis. It also inhibits **matrix metalloproteinases (MMPs)** and apoptosis, contributing to its anti-inflammatory and neuroprotective effects.
各物種劑量
- Hemotropic mycoplasmosis · 6-11 mg/kg PO q12h · PO · q12h · 21 days
- Adjunctive treatment atypical mycobacterial dermal infections · 5-12.5 mg/kg PO, IV q12h · PO, IV · q12h
- Adjunctive treatment of Nocardiosis, Actinomycosis · 5-25 mg/kg PO, IV q12h · PO, IV · q12h
- Susceptible mycobacterial, L-Forms, or mycoplasma infections · 5-12.5 mg/kg PO q12h · PO · q12h
- Bacterial, rickettsial, mycoplasmal and chlamydial diseases · 5-10 mg/kg · PO · q12h · Avoid dry pilling; follow with a water bolus.
- Susceptible soft tissue and urinary tract infections · 5-12 mg/kg PO or IV q12h · PO, IV · q12h · 7-14 days
- Brucellosis · 25 mg/kg PO once daily (q24h) · PO · q24h · 4 weeks · Given with Gentamicin 5 mg/kg SC once daily for 7 days (weeks 1 and 4). Doxycycline can eventually be substituted. May need two or more 4-week courses.
- Adjunctive treatment of Nocardiosis, Actinomycosis · 5-25 mg/kg PO, IV q12h · PO, IV · q12h
- Brucellosis in animals that are housed singly and neutered · 25 mg/kg PO once daily · PO · q24h · 14 days · Given with dihydrostreptomycin at 5 mg/kg IM twice daily for 7 days.
- Ehrlichiosis (E. canis) · 10 mg/kg PO (rarely IV) q12h · PO, IV · q12h · 28 days · For dogs with a positive test result and clinical signs consistent with the infection.
給藥途徑
禁忌症
- Hypersensitivity to tetracyclines
- Pregnant or nursing animals
- Animals less than 6 months old (relative contraindication)
- Pregnancy
- Young, developing animals
不良反應
- Nausea and vomiting (most common)
- Dental or bone staining (if exposed in utero or early life)
- Increases in hepatic enzymes (rare)
- Ototoxicity (rare)
- Urticaria, shivering, hypotension, dyspnea, cardiac arrhythmias, and shock (if given rapidly IV)
- Superinfections (overgrowth of non-susceptible bacteria or fungi)
- Photosensitivity (reported in humans)
- Hepatotoxicity or blood dyscrasias (rare, reported in humans)
- CNS effects like dizziness/lightheadedness (reported in humans)
- Blue-gray pigmentation of skin and mucous membranes (reported in humans)
- Nausea
- Vomiting
- Diarrhoea
- Bone and teeth abnormalities (in developing animals)
- Oesophageal erosions (especially in cats if dry-pilled)
藥物相互作用
- Antacids, Oral (Aluminum, Calcium, Magnesium, Zinc, Bismuth) · Can chelate divalent or trivalent cations, decreasing absorption of the tetracycline. Give at least 12 hours before or after the cation-containing product.
- Bismuth subsalicylate, Kaolin, Pectin · May reduce minocycline absorption.
- Iron, Oral · Decreased tetracycline absorption. Give iron salts 3 hours before or 2 hours after the tetracycline dose.
- Isotretinoin · May increase the risk for nervous system effects when used concurrently.
- Penicillins, Cephalosporins, Aminoglycosides · Bacteriostatic drugs may interfere with the bactericidal activity of these antibiotics (clinical significance is controversial).
- Warfarin · Tetracyclines may depress plasma prothrombin activity; anticoagulant dosage adjustment may be needed.
- Antacids · Reduced absorption of minocycline · moderate
- Calcium salts · Reduced absorption of minocycline · moderate
- Magnesium salts · Reduced absorption of minocycline · moderate
- Iron salts · Reduced absorption of minocycline · moderate
- Sucralfate · Reduced absorption of minocycline · moderate
- Phenobarbital · Increased metabolism of minocycline, decreasing plasma levels · moderate
監測
- Clinical efficacy (resolution of infection)
- Adverse effects (GI upset, signs of hypersensitivity)
- Renal function (if used concurrently with nephrotoxic drugs like gentamicin)
- Clinical efficacy
- Gastrointestinal signs
- Hepatic function (in patients with pre-existing liver disease)
過量
Oral overdoses are most likely associated with **GI disturbances** (vomiting, anorexia, and/or diarrhea). - **Treatment:** Although less vulnerable to chelation than other tetracyclines, oral administration of divalent or trivalent cation antacids may bind some of the drug and reduce GI distress. - **Supportive Care:** Should the patient develop severe emesis or diarrhea, monitor fluids and electrolytes and replace if necessary.
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