ミノサイクリン
ミノサイクリンは、高脂溶性の第2世代**テトラサイクリン系抗生物質**です。血液脳関門を通過し前立腺に移行するなど、優れた組織移行性を持つことで知られています。 - **臨床用途：** ブルセラ症、ライム病、ヘモプラズマ症、非定型抗酸菌感染症、および耐性院内感染症。 - **利点：** 古い水溶性のテトラサイクリン系と比較して、骨や歯の異常を引き起こす可能性が低いです。中等度の腎機能低下がある患者にも用量調整なしで安全に使用できます。 - **その他の特性：** 抗菌作用に加えて、**抗炎症作用**および**神経保護作用**（マトリックスメタロプロテアーゼの阻害など）を示し、血管肉腫などの補助療法として研究されていますが、初期の結果は期待外れでした。
作用機序: 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.
動物種別の用量
- 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.
投与経路
禁忌
- Hypersensitivity to tetracyclines
- Pregnant or nursing animals
- Animals less than 6 months old (relative contraindication)
- Pregnancy
- Young, developing animals
有害事象
- 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)
薬物相互作用
- 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
モニタリング
- 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)
過量投与
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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