Chlorambucil

Chlorambucil is an immunosuppressant prescribed for dogs with certain types of lymphatic cancers and autoimmune diseases. This medication is classified as a cytotoxin, which means it hinders the division of mutated cells. 

Dosage

A typical dose of Chlorambucil for dogs is between 0.05 mg and 0.1 mg per lb. The exact dosage your vet prescribes may vary depending on their specific condition. 

Dosage instructions

Pet parents must be very conscientious about how they give this medication since it can absorb through the skin. Use gloves when handling chlorambucil. Double-bag and dispose of contaminated gloves immediately after administering treatment. 

Efficacy

A clinical study evaluating the efficacy of chlorambucil and prednisolone in dogs with inoperable canine mast cell tumors found that 38% of dogs achieved partial or complete remission with treatment. The study also noted that this combination results in minimal toxicity, making it a viable alternative for dogs unsuitable for surgery or radiotherapy.

However, another study found that higher doses of chlorambucil caused adverse reactions, including gastrointestinal problems and low platelet counts, in a significant number of pets.

Cost

Brand name chlorambucil tablets cost $30 per 2 mg tablet on average. Drug prices may vary depending on costs of living and veterinary care in the area.

Side effects

Cancer drugs are known to have some of the most severe side effects of all medications. Below are some common side effects of chlorambucil for dogs:

• Mouth ulcers

• Bone marrow suppression

• Upset stomach

• Hair loss

• Mood changes

• Severe fatigue

• Abnormal bleeding

• Twitching

• Aggression

• Shortness of breath

• Epilepsy

• Opportunistic infections 

• Low platelet levels

Considerations

Chlorambucil inhibits the ability of bone marrow to generate red blood cells. Never use this medication in combination with another drug that causes myelosuppression. 

Chlorambucil inhibits immune response, which helps control cancer spread but also leaves dogs vulnerable to serious and sometimes deadly opportunistic infections. 

During treatment, you'll need to exercise extreme caution when coming in contact with any of your pet's excretions. Wear gloves and thoroughly clean your hands with hot water and soap after picking up their feces. Remove your gloves carefully so that you aren't touching the contaminated side — double-bag used gloves and any other contaminated waste before throwing them away. 

Clean your skin immediately if your dog licks you — this medication can transfer from their saliva onto your skin. 

Chlorambucil may cause anemia and low red blood cell production. Chlorambucil can also trigger an immune response causing the body to mistake blood platelets for foreign bodies and attack them. Regular check-ups are crucial since your dog's iron levels, platelets, and blood cell counts must be monitored.

Due to the severe side effects, some owners choose not to treat terminal cancers since it can lead to more stress and depression in the animal. Talk to your vet about the pros and cons of using this medication before deciding if it's right for your dog. 

Drug interactions

A lot of medications can interfere with the effects of chlorambucil. Use caution when giving chlorambucil for dogs who are on any of the following drugs: 

• Myelosuppressive agents

• Vaccines

• Adriamycin (doxorubicin)

• Methotrexate

• Carboplatin

• Prednisone

• Albuterol sulfate

• Allopurinol

• Cyclosporine ophthalmic solution

• Lasik

• Bone-marrow suppressants

• Cyclophosphamide

• Losartan

• Antineoplastics

Allergic reactions and sensitivity

Allergic reactions to chemotherapy drugs are not unusual in humans or canines. These reactions happen when the body releases a histamine response toward a substance the body doesn't recognize. These reactions can manifest in many ways, including swelling, itching, rapid heartbeat, welts, wheezing, stomach upset, and weak pulse. Unfortunately, drug allergies are fairly common in humans and animals on anti-cancer drugs. 

Reactions to chemotherapy drugs fall into two main categories: type 1 reactions and anaphylactic shock. Anaphylactic shock is more severe than type 1 since it can cause the entire organ system to shut down from lack of oxygen. Anaphylaxis typically includes symptoms of type 1 reactions in addition to other more serious symptoms. Without immediate treatment, anaphylaxis can cause rapid decline and even death in canines.

Type 1 drug reaction symptoms:

• Rash

• Excessive scratching

• Swelling of the face, mouth, or extremities 

Anaphylactic shock is categorized by:

• A weak, racing pulse

• High blood pressure 

• Difficulty breathing

• Passing out

• Pronounced muscle weakness

Frequently asked questions

What happens if my dog overdoses on chlorambucil?

Take your dog to the vet immediately if you think your dog has ingested too much chlorambucil. Pets who overdose on this medication often need their stomach pumped, and there's only a small window of time during which this treatment can be performed. 

Is chlorambucil a type of chemotherapy?

Yes, chlorambucil is a chemotherapy medication and immunosuppressant. 

How long do the side effects of chlorambucil last for dogs once treatment is complete? 

Side effects of chlorambucil for dogs can last up to a week and a half after finishing treatment. Dogs with low kidney or liver function take longer to excrete the drug and may continue to show side effects for longer. 

Are all canine cancers life-threatening?

No. Many dogs who complete chemotherapy go on to live completely healthy lives.

This medication makes my dog feel worse. Can I just give it to them every other day? 

The most important thing with Chlorambucil is consistency. Your pet must take their dose daily to prevent cell division and slow the cancer spread.