Asparaginase
L-Asparaginase / L-asparagine amidohydrolase
Also known as: Elspar · Crasnitine · Erwinase · Kidrolase · Laspar · Leucogen · Leunase · Paronal · Serasa · coloaspase · A-ase · ASN-ase · L-asparaginase · L-asparagine amidohydrolase · MK-965 · NSC-109229 · L-Asparginase · Crisantaspase
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
This dose is based on body surface area (mg/m²). Convert body weight to body surface area before dosing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Lymphoid malignancies / Leukemia | 400 Units/kg or 10,000 Units/m2 IM or SC, with a maximum dose of 10,000 Units per patient | IM/SC | Protocol dependent | Protocol dependent | 🌎 NA |
| Treatment of lymphoid malignancies | 10,000 IU/m2 or 400 IU/kg | IM/SC | q7d or less frequently | As per chemotherapy protocol | 🌍 EU |
- Lymphoid malignancies / Leukemia: Many oncologists recommend administering diphenhydramine at 2 mg/kg SC 30 minutes prior to administration.
- Treatment of lymphoid malignancies: See specialist texts for chemotherapy protocols and conversion of body weight to body surface area.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Lymphoid malignancies / Leukemia | 400 Units/kg or 10,000 Units/m2 IM or SC, with a maximum dose of 10,000 Units per patient | IM/SC | Protocol dependent | Protocol dependent | 🌎 NA |
| Treatment of lymphoid malignancies | 10,000 IU/m2 or 400 IU/kg | IM/SC | q7d or less frequently | As per chemotherapy protocol | 🌍 EU |
- Lymphoid malignancies / Leukemia: Many oncologists recommend administering diphenhydramine at 1 mg/kg SC 30 minutes prior to administration.
- Treatment of lymphoid malignancies: See specialist texts for chemotherapy protocols and conversion of body weight to body surface area.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Asparaginase is a unique, enzyme-based antineoplastic agent primarily used in veterinary oncology to treat lymphoid malignancies (such as lymphoma) and leukemias (especially Acute Lymphoblastic Leukemia or ALL) in dogs and cats.
Unlike traditional chemotherapy drugs that directly damage DNA, asparaginase works by starving cancer cells of a vital nutrient. Because it generally spares the bone marrow (minimal myelosuppression) and gastrointestinal mucosa, it is an excellent choice for induction protocols or as a "rescue" therapy when a patient's bone marrow is already compromised.
Clinical Pearl: Because asparaginase is a large, foreign protein (derived from E. coli), hypersensitivity/anaphylaxis is a major clinical concern. Furthermore, its efficacy often drops over time due to the patient's immune system producing neutralizing antibodies against the enzyme.
Mechanism of action
Normal cells can synthesize their own asparagine using the enzyme asparagine synthetase. However, many lymphoid malignant cells lack this enzyme and rely entirely on exogenous asparagine from the bloodstream for protein and DNA synthesis.
Asparaginase is an enzyme that circulates in the intravascular space and catalyzes the breakdown of circulating asparagine: L-asparagine + H2O → (via L-asparaginase) → Aspartic acid + Ammonia
By rapidly depleting circulating asparagine, the drug halts protein synthesis in the tumor cells, leading to apoptosis. The antineoplastic activity is greatest during the post-mitotic (G1) phase of the cell cycle.
Safety & warnings
Contraindications
- Patients with a history of anaphylaxis to asparaginase
- Patients with pancreatitis or a history of pancreatitis
Adverse effects
- Hypersensitivity reactions (vomiting, diarrhea, urticaria, pruritus, dyspnea, hypotension, collapse)
- Hemorrhagic pancreatitis
- Hepatotoxicity
- Coagulation defects
- Hyperglycemia (secondary to altered insulin synthesis)
- Leukopenia (rare)
Precautions
Use with caution in patients with preexisting hepatic, renal, hematologic, gastrointestinal, or CNS dysfunction. Intravenous (IV) administration is generally avoided as it significantly increases the risk of anaphylaxis. Premedication with an antihistamine (e.g., diphenhydramine) is strongly recommended. Asparaginase can be a contact irritant; wash off any inadvertent skin contact. May alter thyroid function tests by decreasing thyroxine-binding globulin (TBG).
Drug interactions
Asparaginase may reduce methotrexate effectiveness against tumor cells until serum asparagine levels return to normal.
Concurrent use may increase the risk for hyperglycemia.
Increased toxicity (neuropathy and erythropoiesis disruption) and myelosuppression may occur. Some oncologists recommend separating the dosing by a few days to a week.
Monitoring
- Hepatic function
- Renal function (BUN may be increased by drug action)
- Pancreatic function (blood glucose, amylase)
- Hematopoietic function
- Patient observation for hypersensitivity during and immediately after administration
- Serum ammonia (may be increased)
Pharmacokinetics
Absorption
Not absorbed from the GI tract. After IM injection, serum levels are approximately 50% of those achieved after IV injection.
Distribution
Due to its high molecular weight, it does not diffuse readily out of capillaries; about 80% of the drug remains within the intravascular space.
Metabolism
The metabolic fate of asparaginase is not known.
Elimination
Unknown.
Overdose
In dogs, the maximally tolerated dose is 10,000 IU/kg and the lethal dose is 50,000 IU/kg. Overdosage is expected to cause severe toxicity secondary to protein synthesis alteration (pancreatitis, hepatotoxicity, coagulopathy). Treatment is supportive.
Available products
Formulations
- Powder for Injection (lyophilized)
Human-labeled
- Asparaginase Powder for Injection, lyophilized: 10,000 Units in 10 mL vials (with 80 mg mannitol, preservative-free) (Elspar)
Regulatory status
POM (Prescription Only Medicine)
POM-V
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store powder for injection at < 8°C; stable for at least 48 hours at room temperature. After reconstitution, the manufacturer states it is stable refrigerated for up to 8 hours (other sources state up to 14 days). Solutions should be clear; discard if turbid. Do not shake vigorously during reconstitution to avoid foaming and loss of potency.
Client information
Important: Asparaginase is a chemotherapy drug, but it works differently than most and usually does not cause severe drops in white blood cell counts.
- Allergic Reactions: Because this drug is a protein derived from bacteria, allergic reactions (panting, facial swelling, vomiting, restlessness, collapse) can occur, usually right after the injection. We will often give an antihistamine beforehand to help prevent this.
- Pancreas and Liver: It can occasionally cause inflammation of the pancreas (pancreatitis) or liver issues. Watch closely for severe vomiting, diarrhea, abdominal pain, or yellowing of the eyes/gums.
- Bleeding: Contact your vet immediately if you notice unexplained bruising, bleeding gums, or bloody diarrhea.
- Safety: Your pet's waste may contain traces of the drug for a few days. Follow your oncologist's guidelines for safe handling of urine and feces.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.