암피실린

항생제 - 아미노페니실린Critically Important

**암피실린(Ampicillin)**은 광범위, 시간 의존성, 살균성 아미노페니실린계 항생제입니다. 주요 약리학적 특징: * **항균 스펙트럼:** 많은 그람 양성균(페니실린 감수성 장구균인 *E. faecium* 포함), 혐기성균(*Clostridium* spp. 등), 일부 그람 음성 호기성균(*E. coli*, *Klebsiella*, *Haemophilus*, *Proteus mirabilis*)에 효과적입니다. * **내성:** 천연 페니실린과 마찬가지로 **베타락타마제 생성 세균**(*Staphylococcus aureus* 등)에 의해 쉽게 불활성화됩니다. 녹농균, 세라티아, 엔테로박터 및 비정형 원인균(마이코플라스마, 리케차, 진균)에는 효과가 없습니다. * **임상적 유용성:** 소동물에서 경구용 암피실린은 생체이용률이 더 높은 아목시실린으로 대체되었으나, 주사용 암피실린은 여전히 중요한 치료제입니다. * **염 형태:** * **암피실린 나트륨(Sodium):** 수용성이 높아 정맥(IV) 투여에 적합하며, 빠르고 높은 최고 혈청 농도를 제공합니다. * **암피실린 삼수화물(Trihydrate):** 근육(IM) 또는 피하(SC) 투여용 저장성 제제로, 흡수가 느리고 최고 혈청 농도가 낮습니다(나트륨염의 약 절반). 전신 감염 치료를 위해 높은 최소억제농도(MIC)가 요구되는 경우에는 사용하지 않아야 합니다.

작용 기전: Ampicillin is a **beta-lactam antibiotic** that exerts its bactericidal effect by interfering with bacterial cell wall synthesis. * **Mechanism:** Ampicillin covalently binds to specific **Penicillin-Binding Proteins (PBPs)** (primarily transpeptidases) located inside the bacterial cell wall. * **Pathway:** Binding to PBPs → inhibition of the final transpeptidation step of peptidoglycan cross-linking → weakening of the cell wall structure → activation of endogenous autolytic enzymes (autolysins) → **osmotic lysis and bacterial cell death**. * **Pharmacodynamics:** Efficacy is **time-dependent**, meaning the free drug concentration must remain above the Minimum Inhibitory Concentration (MIC) for a significant portion of the dosing interval (typically >40-50% of the interval).

동물 종별 용량

Dogs

Gram-positive infections · 10-20 mg/kg PO twice daily; 5 mg/kg IM, SC twice daily; 5 mg/kg IV three times daily · PO/IM/SC/IV · q8h-q12h
Gram-negative infections · 20-30 mg/kg PO three times daily; 10 mg/kg IM, SC three times daily; 10 mg/kg IV four times daily · PO/IM/SC/IV · q6h-q8h
Susceptible UTI's · 12.5 mg/kg PO q12h for 3-7 days, 6.6 mg/kg IM or SC q12h for 3-7 days · PO/IM/SC · q12h · 3-7 days
Susceptible soft tissue infections · 10-20 mg/kg PO, IM or SC q8h for 7 days · PO/IM/SC · q8h · 7 days
Pneumonia, systemic · 22 mg/kg PO, IV or SC q8h for 7-14 days · PO/IV/SC · q8h · 7-14 days
Meningitis, orthopedic infections · 22 mg/kg PO, IV, IM, SC q6-8h as long as necessary · PO/IV/IM/SC · q6-8h · As long as necessary
Susceptible sepsis, bacteremia · 20-40 mg/kg IV, IM or SC q6-8h for as long as necessary · IV/IM/SC · q6-8h · As long as necessary
Neonatal sepsis · 50 mg/kg IV or intraosseous q4-6h as long as necessary · IV/Intraosseous · q4-6h · As long as necessary
Sepsis · 20-40 mg/kg IV q6-8h · IV · q6-8h
Susceptible UTI's · 25 mg/kg PO q8h · PO · q8h
To eliminate the leptospiremic phase of leptospirosis · 22 mg/kg q6-8h IV during the acute illness until patient is eating, then amoxicillin 22 mg/kg PO q8h · IV · q6-8h · During acute illness · Followed by oral amoxicillin

투여 경로

POIMIVSCIntraosseousIntrauterine

금기

Patients with a known hypersensitivity to penicillins
Oral administration in patients with septicemia, shock, or grave illness (due to delayed/diminished GI absorption)
Oral or parenteral use in small hindgut fermenters (rabbits, guinea pigs, chinchillas, hamsters) due to risk of fatal clostridial enterotoxemia

이상반응

Gastrointestinal upset (anorexia, vomiting, diarrhea)
Antibiotic-associated diarrhea and superinfections (alteration of gut flora)
Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
Neurotoxicity (ataxia, seizures) at very high doses or prolonged use
Elevated liver enzymes (rare)
Tachypnea, dyspnea, edema, and tachycardia (reported in dogs)

약물 상호작용

Bacteriostatic Antimicrobials (e.g., chloramphenicol, macrolides, tetracyclines) · Potential in vitro antagonism; clinical significance is debated but concurrent use is traditionally discouraged.
Methotrexate · Ampicillin may decrease the renal excretion of methotrexate, leading to increased levels and potential toxicity.
Probenecid · Competitively blocks the tubular secretion of penicillins, increasing serum levels and prolonging half-life.
Aminoglycosides (e.g., gentamicin, amikacin) · In vitro inactivation of aminoglycosides if mixed in the same syringe or fluid bag. May also occur in vivo in patients with severe renal failure.
Tetracycline · Antagonism of bactericidal effect due to bacteriostatic action · moderate
Erythromycin · Antagonism of bactericidal effect due to bacteriostatic action · moderate
Chloramphenicol · Antagonism of bactericidal effect due to bacteriostatic action · moderate
Aminoglycosides · In vitro inactivation if mixed in the same syringe; however, exhibits synergistic antimicrobial effects when used concurrently in vivo · major

모니터링

Clinical efficacy (resolution of infection signs)
Adverse effects (GI signs, hypersensitivity reactions)
Therapeutic drug monitoring is not routinely required due to the wide therapeutic index

과용량

Acute oral penicillin overdoses are unlikely to cause significant problems other than **gastrointestinal distress** (vomiting, diarrhea, anorexia). In humans, very high dosages of parenteral penicillins, particularly in patients with underlying renal disease, have induced **CNS effects** (e.g., seizures, ataxia). Treatment is generally supportive and symptomatic.

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