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ペニシリンG

Penicillin G

Benzylpenicillin

抗生物質 - 天然ペニシリンIV (Aqueous Na/K salts only)IMSCPOIntramammaryTopical (guttural pouch instillation)犬猫小型哺乳類フェレット鳥馬牛豚

別名: Bicillin C-R · Masti-Clear · Permapen · Pfizerpen · Go-Dry · crystalline penicillin G · APPG · aqueous penicillin · procaine benzylpenicillin

VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス

監査済み v13 用量エビデンス

構造化された用量計算エビデンス

Susceptible infections (extra-label): Penicillin G procaine

20000–40000 units/kgIM

認証済み獣医師の確認が必要

  • q12-24h

NA

必ず考慮する臨床コンテキスト (4)
  • NOTE: Label dosages of penicillin have been unchanged for decades and may result in marked underdosing based on current understanding of antibiotic therapy. Although consideration of the label recommendations is required, present-day recommended dosing regimens should be used.
  • ■ Because penicillins usually have minimal toxicity associated with their use, monitoring for efficacy is usually all that is required unless toxic signs develop. Serum concentrations and therapeutic drug monitoring are not routinely done with these agents.
  • Penicillin G procaine should be stored at 2°C to 8°C (36°F-46°F); avoid freezing. Penicillin G benzathine should be stored at 2°C to 8°C (36°F-46°F).
  • Penicillin G sodium and potassium powder for injection can be stored at room temperature (15°C-30°C [59°F-86°F]). After reconstituting, the injectable solution is stable for 7 days when kept refrigerated (2°C-8°C [36°F-46°F]) and for 24 hours at room temperature.
高リスク認証済み獣医師の確認が必要formularyプロトコル 2023監査 dose-audit-plumb-v13

用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。

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概要

​ペニシリンG​（ベンジルペニシリン）は、Penicillium chrysogenumから得られる狭域スペクトルの天然β-ラクタム系抗生物質です。ほとんどの​グラム陽性好気性菌​（レンサ球菌、ペニシリナーゼ非産生ブドウ球菌など）、一部のグラム陰性菌（パスツレラなど）、および多くの​嫌気性菌​（クロストリジウムなど）に対して高い有効性を示します。

​臨床のポイント：​ ペニシリンGの塩の形態により、投与経路と薬物動態プロファイルが決定されます：

  • ​水溶性塩（ナトリウムまたはカリウム）：​ 静脈内（IV）または筋肉内（IM）投与用。急速に高い血清中ピーク濃度に達しますが、半衰期が非常に短いため、頻回投与（例：4〜6時間ごと）が必要です。
  • ​持続性塩（プロカインおよびベンザチン）：​ 懸濁液として製剤化されており、​筋肉内（IM）または皮下（SC）投与専用​です（静脈内投与は厳禁）。プロカインは12〜24時間持続するデポ効果をもたらし、ベンザチンは数日間持続する非常に低く延長された濃度を提供します。

ペニシリンGは、多くのブドウ球菌やグラム陰性腸内細菌が産生するβ-ラクタマーゼ（ペニシリナーゼ）酵素による分解を受けやすいです。

作用機序

Penicillin G is a time-dependent bactericidal antibiotic.

  • It covalently binds to ​Penicillin-Binding Proteins (PBPs)​ located on the inner membrane of the bacterial cell wall.
  • This binding → inhibits the transpeptidation enzyme responsible for cross-linking peptidoglycan strands.
  • Failure of cell wall synthesis → activation of autolytic enzymes within the cell wall → osmotic lysis and bacterial death.

Because it targets cell wall synthesis, it is most effective against actively dividing bacteria.

安全性・警告

禁忌

  • Known hypersensitivity to penicillins or cephalosporins
  • Intravenous administration of Procaine or Benzathine suspension formulations
  • Oral administration in horses and hindgut fermenters (rabbits, guinea pigs) due to risk of fatal dysbiosis (unless specifically indicated, e.g., calves with clostridial enteritis)

有害事象

  • Hypersensitivity reactions (anaphylaxis, urticaria, rash)
  • Gastrointestinal upset (anorexia, vomiting, diarrhea) with oral use
  • Procaine toxicity (CNS excitement, seizures) in small birds and horses if inadvertently given IV
  • Pain or tissue reaction at IM injection sites

注意事項

Use cautiously in small birds as procaine penicillin may cause procaine toxicity. Do not use oral penicillin therapy in horses for systemic infections (e.g., botulism). Ensure repository forms (procaine/benzathine) are never administered intravenously. Monitor for hypersensitivity reactions. High doses of Penicillin G Potassium given rapidly IV can cause hyperkalemia and cardiac arrhythmias.

医薬品相互作用

Bacteriostatic Antibiotics (e.g., Tetracyclines, Macrolides)

May antagonize the bactericidal activity of penicillins, which require actively dividing cells to be effective.

Aminoglycosides (e.g., Amikacin, Gentamicin)

In vivo synergy against certain bacteria; however, physically incompatible if mixed in the same syringe or IV line (inactivation of the aminoglycoside).

Probenecid

Competitively inhibits renal tubular secretion of penicillins, significantly prolonging their half-life and increasing serum concentrations.

監視

  • Clinical efficacy (resolution of infection signs)
  • Signs of toxicity or hypersensitivity (anaphylaxis, rash)
  • Electrolytes (if using high doses of Na or K salts IV)

薬物動態

半減期

猫Aqueous: ~0.5 hours馬Aqueous: ~0.5 - 1 hour犬Aqueous: ~0.5 hours

吸収

Oral absorption is generally poor and variable due to degradation by gastric acid. Aqueous salts (Na/K) are rapidly absorbed after IM/SC injection. Procaine and benzathine salts are slowly absorbed from IM injection sites, providing prolonged but lower serum concentrations.

分布

Widely distributed to most tissues (lungs, kidneys, muscle, bone). Poor penetration into the central nervous system (CNS), eye, and prostate unless severe inflammation is present. Crosses the placenta.

代謝

Minimal hepatic metabolism.

消失

Rapidly excreted primarily unchanged in the urine via active renal tubular secretion and glomerular filtration.

過剰投与

Because penicillins usually have minimal toxicity associated with their use, monitoring for efficacy is usually all that is required unless toxic signs develop.

​Clinical Pearl:​ Massive overdoses, particularly of aqueous salts given rapidly IV, can lead to neuromuscular hypersensitivity, seizures, or electrolyte imbalances (hyperkalemia with potassium salt, hypernatremia with sodium salt). Treatment is supportive.

製品

製剤

  • Powder for injection (Potassium or Sodium salts)
  • Suspension for injection (Procaine or Benzathine salts)
  • Oral tablets and powder for solution
  • Intramammary infusion syringes

動物用医薬品

  • Penicillin G Procaine Injection 300,000 Units/mL
  • Penicillin G Procaine Mastitis Syringes 100,000 Units/mL (Go-Dry, Masti-Clear)
  • Penicillin G Benzathine 150,000 Units/mL with Penicillin G Procaine 150,000 Units/mL Injection

ヒト用医薬品

  • Penicillin G (Aqueous) Sodium Powder for Injection: 5,000,000 Units & 20,000,000 Units
  • Penicillin G (Aqueous) Potassium Injection: 1,000,000 Units, 2,000,000 Units & 3,000,000 Units
  • Penicillin G Procaine Injection: 600,000 Units/vial & 1,200,000 Units/vial
  • Penicillin G Benzathine Injection: 600,000, 1,200,000, & 2,400,000 Units/dose
  • Penicillin G Benzathine/Penicillin G Procaine IM Injection (Bicillin C-R)

規制ステータス

規制データなし: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

保管・安定性

Penicillin G sodium and potassium powders should be protected from moisture. Oral powder for solution: store at room temperature before mixing; after reconstituting, refrigerate (2-8°C) and discard after 14 days. Injectable Na/K solutions: stable for 7 days refrigerated (2-8°C) and 24 hours at room temperature. Procaine and Benzathine suspensions should be stored at 2-8°C; avoid freezing.

飼主向け情報

  • ​投与方法：​ 経口ペニシリンは、吸収を最大化するために​空腹時​（食前1時間または食後2時間）に投与してください。ペットが胃腸の不調（嘔吐、食欲不振）を起こした場合は、少量の食事と一緒に与えても構いません。
  • ​服薬遵守：​ ペットが完全に元気になったように見えても、​処方された薬は最後まで必ず飲み切る​ことが非常に重要です。途中でやめると、耐性菌が発生する原因になります。
  • ​アレルギー反応：​ 顔の腫れ、じんましん、発疹、呼吸困難などのアレルギー反応の兆候に注意してください。これらの症状が現れた場合は、直ちに獣医師に連絡してください。
  • ​注射部位：​ 注射剤を使用している場合、注射部位が痛んだり腫れたりすることがあります。

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