Heartworm side effects

Question
Hi,

I had my dog trixie treated for heartworms on September 14th, she was sent home on the 16th. I noticed a week later she had developed a lump on the injection site which is about the size of my palm. I took her back to the vet and they stated this is a side effect and gave me predisone and a steroid to give trixie twice a day for a week, it has been 4 days and i have not seen any improvement. Is this common or is this more serious? She is eating and drinking normal but I am a little concern that this is something more serious then common. Thanks, Billie Jo

Answer
It is not more serious and certainly not as serious as a reaction to the drug. It will take longer then 4 days because it is a large irritation and it has to resolve. It may take weeks, so have some patience with it.

If it isn't gone in about three-four weeks you need to let your vet know it. If it gets worse then they need to contact Merial who make the injectable treatment (Melarsomine) that they used. Sometimes they will help with the cost of treatment if the lump gets so big that it ulcerates.

This is what the insert for the drug says:
Injection Sites: At the recommended dosage in clinical field trials, significant irritation was observed at the intramuscular injection sites, accompanied by pain, swelling, tenderness, and reluctance to move. Approximately 30% of treated dogs experienced some kind of reaction at the injection site(s).

Your bigger worries right now is that she stay calm and not run all over the place so that these dying worms don't exit her heart all at once. Predinose is a steroid so did he give you two steroids?

I am sure this will resolve itself with time.