AE,
Ivermectin is a treatment and preventative measure for ticks/fleas/heartworm. It is much much cheaper than frontline, heartgauard and the assorted collars, drops, pills that are also good treatments. Ivermectin takes a bit more more work than a pill or a drop but the cost savings more than make up for the inconvenience. Ivermectin is readily available and a 50ml bottle with syringe (depending on the number of dogs/dosages will last a long time - let's say a year) costs $RD300 or less.
I personally use ivermectin at least once a month, and attach a flea/tick collar to each dog. Neither the collar nor the Ivermectin will prevent fleas/ticks from getting on your pets, but will kill them and effectively interrupt the lifecycle if administered properly.
I'm not a vet and for a serious infestation its always prudent to seek advice from a professional. However, for monthly prevention and ongoing treatment of fleas/ticks and heartworm, Ivermectin seems to be a commonly and routinely used medication, that is easy to use, is stored in the refrigerator, is effective and is really cheap when compared to the cost of drops.
Some dogs and some breeds may be intolerant of ivermectin. Read up on the internet and then talk a vet. They will tell you the best way to ensure your pets can use ivermectin.