ラニチジン

Ranitidine

Ranitidine hydrochloride

H2受容体拮抗薬 / 消化管運動促進薬POIVIMSC犬猫小型哺乳類フェレット馬

別名: Zantac 75 · Zantac EFFERdose · AH-19065 · ranitidini hydrochloridum · Ranitidinum

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

1-2 mg/kgPO· twice daily

体重— 🐕

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。

動物種別用量

🌎 NA — North America🌍 EU — Europe

犬

適応	用量	経路	頻度	期間	地域
For esophagitis	1-2 mg/kg	PO	twice daily	—	🌎 NA
For chronic gastritis	0.5 mg/kg	PO	twice daily	—	🌎 NA
For ulcer disease	0.5-2 mg/kg	PO, IV or IM	q8-12h	—	🌎 NA
For ulcer disease	2 mg/kg	PO, IV	q8h	—	🌎 NA
For ulcer disease (also used for esophagitis)	1-2 mg/kg	PO, IV, SC	q12h	—	🌎 NA
For ulcer disease	2 mg/kg	PO, IV	q12h	—	🌎 NA
For gastrinoma	1-2 mg/kg	PO, SC, IV	q8-12h	—	🌎 NA
For gastrinoma	0.5 mg/kg	PO, IV or SC	twice daily	—	🌎 NA
To treat hypergastrinemia secondary to chronic renal failure	1-2 mg/kg	PO	twice daily	—	🌎 NA
To treat hyperhistaminemia secondary to mast cell tumors	2 mg/kg	PO/IV/IM/SC	q12h	—	🌎 NA
As a prokinetic agent to stimulate gastric contractions	1-2 mg/kg	PO	q12h	—	🌎 NA
All uses (ulcers, gastritis, prokinetic)	2 mg/kg	slow IV, SC, PO	q8-12h	Typically 1 month for ulcers (2 weeks post-remission)	🌍 EU

To treat hyperhistaminemia secondary to mast cell tumors: Route not explicitly specified in this line of monograph, typically PO/injectable
All uses (ulcers, gastritis, prokinetic): Absorption is not clinically significantly affected by food intake.

猫

適応	用量	経路	頻度	期間	地域
For ulcer disease/esophagitis	2.5 mg/kg IV q12h or 3.5 mg/kg PO q12h	IV, PO	q12h	—	🌎 NA
For ulcer disease/esophagitis	1-2 mg/kg	PO, IV, SC	q12h	—	🌎 NA
For ulcer disease/esophagitis	2 mg/kg	PO, IV	q12h	—	🌎 NA
As a prokinetic agent to stimulate colonic motility	1-2 mg/kg	PO	q8-12h	—	🌎 NA
As a prokinetic agent to stimulate colonic motility	1-2 mg/kg	PO	q12h	—	🌎 NA
All uses	2 mg/kg/day	IV	constant infusion	—	🌍 EU
All uses	2.5 mg/kg	IV	Not specified	—	🌍 EU

All uses: Not an effective acid suppressant in healthy cats.
All uses: Not an effective acid suppressant in healthy cats.

小型哺乳類

適応	用量	経路	頻度	期間	地域
As a prokinetic in rabbits	0.5 mg/kg	IV	q24h	—	🌎 NA
For suspected gastric ulceration in rabbits	2-5 mg/kg	PO	twice daily	—	🌎 NA

As a prokinetic in rabbits: Used with cisapride (0.5 mg/kg PO q8h).

フェレット

適応	用量	経路	頻度	期間	地域
For Helicobacter mustelae	24 mg/kg	PO	q8-12h	14 days	🌎 NA

For Helicobacter mustelae: Uses Ranitidine bismuth citrate (must be compounded). Given with clarithromycin (12.5 mg/kg PO q8-12h).

馬

適応	用量	経路	頻度	期間	地域
Foals	1.5 mg/kg IV q8h or 6.6 mg/kg PO q8h	IV, PO	q8h	—	🌎 NA
Foals	6.6 mg/kg IV q4h or 0.8-2.2 mg/kg IV four times a day; 5-10 mg/kg PO two to four times a day.	IV, PO	q4h or QID (IV); BID-QID (PO)	—	🌎 NA
Adults	1.5-2 mg/kg IV or IM q6-8h; 6.6 mg/kg PO q8h	IV, IM, PO	q6-8h (IV/IM); q8h (PO)	—	🌎 NA

Foals: Often used with omeprazole (4 mg/kg PO q24h).

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。

診察中ですか？VetSheet の AI が薬剤・用量・投与期間を構造化された診察記録に直接記入します。VetSheet の仕組みを見る

概要

ラニチジン（Ranitidine）は、獣医療で広く使用されている競合的ヒスタミンH2受容体拮抗薬および消化管運動促進薬です。

主な臨床的特徴：

胃酸分泌抑制： 胃潰瘍、第四胃潰瘍、十二指腸潰瘍、尿毒症性胃炎、およびストレスや薬物誘発性のびらん性胃炎の治療と予防に使用されます。
消化管運動促進作用： H2ブロッカーの中ではユニークなことに、ラニチジンは消化管運動を刺激するため、胃排出遅延や猫の結腸活動の促進（巨大結腸症など）に有用です。
全身性肥満細胞症： 肥満細胞腫（大量のヒスタミンを放出する）に関連する胃酸過分泌状態の管理に役立ちます。

臨床のポイント： ラニチジンはシメチジンと比較してモルベースで3〜13倍強力です。さらに、肝臓のシトクロムP450酵素をほとんど阻害しないため、薬物相互作用が著しく少なく、複数の薬剤を服用している患者にとってより安全な選択肢となります。

作用機序

Ranitidine exerts its effects via two distinct mechanisms:

Gastric Acid Suppression: It competitively inhibits histamine at the H2 receptors located on the basolateral membrane of gastric parietal cells.
- Histamine blockade → decreased intracellular cAMP → reduced activation of the H+/K+ ATPase (proton pump) → significant reduction in both basal and stimulated gastric acid and pepsin secretion.
Prokinetic Effect: It reversibly inhibits acetylcholinesterase (AChE) in the gastrointestinal tract.
- AChE inhibition → decreased breakdown of acetylcholine → increased acetylcholine (ACh) at muscarinic receptors → stimulation of GI smooth muscle motility and increased lower esophageal sphincter pressure.

安全性・警告

禁忌

Hypersensitivity to ranitidine
No specific contraindications available in the monograph

有害事象

Vomiting (associated with rapid IV boluses in small animals)
Pain at the injection site (IM administration)
Mental confusion (rare, documented in humans)
Headache (rare, documented in humans)
Agranulocytosis (rare)
Transient cardiac arrhythmias (if given too rapidly IV)
Cardiac arrhythmias (rare, typically with rapid IV)
Hypotension (rare, typically with rapid IV)

注意事項

Use cautiously and consider reduced dosages in patients with diminished renal function or hepatic insufficiency, as the drug may accumulate.

Geriatric patients may be more susceptible to adverse effects.

High-dose, chronic IV therapy (longer than 5 days) has caused increased serum ALT levels in humans; monitoring liver enzymes is recommended in these scenarios.

Use with caution in nursing veterinary patients, as ranitidine is excreted in breast milk (milk:plasma ratio of 5:1 to 12:1).

医薬品相互作用

Acetaminophen

Ranitidine (dose-dependent) may inhibit acetaminophen metabolism.

AntacidsModerate

High doses may decrease the absorption of ranitidine; administer at least 2 hours apart.

Ketoconazole

Absorption of ketoconazole may be reduced secondary to increased gastric pH.

Itraconazole

Absorption of itraconazole may be reduced secondary to increased gastric pH.

Metoprolol

Ranitidine may increase metoprolol half-life and peak serum levels.

Nifedipine

Ranitidine may increase nifedipine AUC by 30%.

Propantheline

Delays the absorption but increases the peak serum level of ranitidine; relative bioavailability may be increased by 23%.

Vitamin B-12

Long-term ranitidine use may reduce oral absorption of Vitamin B-12.

SucralfateMinor

May affect absorption; advisable to administer sucralfate 2 hours before H2 blockers

DigoxinModerate

Ranitidine may reduce absorption or effect; stagger oral doses by 2 hours

MetoclopramideModerate

Ranitidine may reduce absorption or effect; stagger oral doses by 2 hours

監視

Clinical efficacy (resolution of clinical signs, improved appetite, absence of blood in feces/vomitus)
Endoscopic examination (if indicated for ulcer healing)
Serum ALT values (consider monitoring during high-dose, chronic IV therapy)
Resolution of gastrointestinal clinical signs
Heart rate and blood pressure (during IV administration)

薬物動態

半減期

犬2.2 hours

吸収

Dogs: Oral bioavailability is ~81%. Horses: Oral bioavailability is ~27% in adults and 38% in foals. Peak levels occur in 100 mins (adults) and 60 mins (foals). Humans: Rapidly absorbed but undergoes extensive first-pass metabolism (net bioavailability ~50%). Food does not appreciably alter absorption.

分布

Widely distributed throughout the body. Volume of distribution: 2.6 L/kg (dogs), 1.1 L/kg (adult horses), 1.5 L/kg (foals). Only 10-19% bound to plasma proteins. Distributes into milk at 25-100% of plasma levels.

代謝

Metabolized in the liver to inactive metabolites.

消失

Excreted in the urine by the kidneys via glomerular filtration and tubular secretion. Clearance in horses is ~10 mL/min/kg (adults) and 13.3 mL/min/kg (foals).

過剰投与

Clinical experience with ranitidine overdosage is limited, but the drug has a wide margin of safety.

Signs of Toxicity: In laboratory animals, massive doses (225 mg/kg/day) have caused muscular tremors, vomiting, and rapid respirations. Single doses of 1 gram/kg in rodents were not fatal.
Treatment: Handle using standard protocols for oral drug ingestions (e.g., gastric decontamination if recent and appropriate). Treat clinical signs symptomatically and supportively. Hemodialysis and peritoneal dialysis can effectively remove ranitidine from the body.

製品

製剤

Effervescent oral tablets
Oral solution
Injection
Injectable: 25 mg/ml solution
Oral: 75 mg tablet
Oral: 150 mg tablet
Oral: 300 mg tablet
Oral: 15 mg/ml syrup

動物用医薬品

None (No veterinary-labeled products currently available)

ヒト用医薬品

Ranitidine HCl Oral Tablets: 75 mg, 150 mg & 300 mg (Zantac, Zantac 75, generic)
Ranitidine HCl Effervescent Oral Tablets: 25 mg & 150 mg (Zantac EFFERdose)
Ranitidine HCl Solution: 15 mg/mL (Zantac, generic)
Ranitidine HCl Injection: 1 mg/mL (premixed) & 25 mg/mL (Zantac, generic)
Ranitidine 75 mg, 150 mg, 300 mg tablets
Ranitidine 15 mg/ml syrup
Ranitidine 25 mg/ml injectable solution

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

🐕 Dogs🐈 Cats

POM (Prescription Only Medicine)

United Kingdom✓ 承認済み処方箋医薬品VMD

🐕 Dogs🐈 Cats

POM (Prescription Only Medicine)

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

保管・安定性

Store tablets in tight, light-resistant containers at room temperature. Store injectable products protected from light at temperatures less than 30°C. A slight darkening of the injectable solution does not affect potency. Injection is stable up to 48 hours when mixed with commonly used IV solutions (including 5% sodium bicarbonate).

飼主向け情報

ラニチジンは、胃酸を減らし、食物が消化管をスムーズに通過するのを助けるために使用される薬です。

投与方法： 獣医師の指示通りに正確に投与してください。投与を忘れると胃酸レベルがリバウンドし、症状が再発する可能性があるため、スキップしないでください。
タイミング： 食事と一緒でも、空腹時でも投与できます。ペットが制酸薬も服用している場合は、ラニチジンから少なくとも2時間空けて投与してください。
副作用： ラニチジンは一般的に非常に安全で、よく耐容されます。副作用はまれですが、軽度の胃腸の不調が見られることがあります。
保管： 錠剤は密閉容器に入れ、直射日光を避けて室温で保管してください。

注意： ラニチジンはシメチジンなどの古い制酸薬よりも薬物相互作用が少ないですが、新しい薬やサプリメントを与える前には必ず獣医師に相談してください。

VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。