Brief:
Just a local inflammation.
Detailed:
Hello
Thank You for contacting HCM.
Welcome to Health Care Magic.
My name is Dr Muhammad Ahmad & i will look into your problem.
I have gone through your query and would try to help you in the best possible way.
Every one reacts to a medicine differently some won't feel a pinch some would feel mild burning which goes away and some may have such a strong
allergic reaction that their life gets endangered.
IN THIS CASE:
In my opinion you probably pushed the drug too rapidly or your BF's veins showed local inflammatory reaction to the drug so it burnt and with time as the drug distributed in whole body so local burning got reduced,as local concentration of the drug reduced.
There is nothing to worry.
SOLUTION:
1- Dilute the drug with sterile water the next time
2-Push it slow over two three mins
Hope this answers your question. If you have additional questions or follow
up questions then please do not hesitate in writing to us.
Wishing you good health