The pup's vet visit should also be for the purpose of getting a heartworm "preventative" or a prescription for a heartworm "preventative". The "preventatives" kill immature heartworms and thereby "prevent" adult heartworms. The term "preventative" is used to differentiate a heartworm "preventative" from a heartworm "treatment". Heartworm "treatments" kill adult heartworms with arsenic compounds and are very hard on a dog.
Interceptor (a heartworm "preventative") will kill most immature heartworms, plus intestinal worms (roundworms, hookworms, whipworms, and Taenia tapeworms), with only one chemical.
Heartgard Plus does the same thing as Interceptor, except
- it does not kill whipworms,
- it uses one chemical for heartworms and a second for intestinal worms, and
- the heartworm chemical has been lowered (too far for total effectiveness?) so that herding breeds can tolerate it.
Both Interceptor and Heartgard Plus are out of a dog's bloodstream within 24-48 hours. Revolution stays in the dog's bloodstream until the next dose and I wouldn't use such a product. If at all possible the kidneys and liver should not have to deal with chemicals on a daily basis.
NOTE: Have a heartworm check done 6 months after starting a "preventative". Immature heartworms that are too old for a "preventative" to kill can not be detected until they become mature adults. After the first check, subsequent checks should be done yearly.