Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry that your dog is constipated. A week is a long time for a dog not to have a bowel movement but I do have a few suggestions which may help. The oral options that I've listed are ones which may help to prevent future episodes; they aren't likely to help resolve the problem at this point since so much time has passed since he's produced stool.
1. Sometimes if you can remove enough hard feces that are present right at the anal opening, the patient is able to evacuate the remainder. So, if you'd like to try and remove fecal material, the following is how you would do so: Place a latex glove on your hand and lubricate it really well with K/Y jelly or Petroleum Jelly and lubricate his rectum, too. Gently insert your index finger into his anus up to your first or second knuckle, and hook your finger into fecal material and gently retract it. You may need to perform this procedure several times.
I would have someone helping you since this may be a little uncomfortable for him and you don't want to get injured yourself.
Ii understand that this is not something that everyone will feel comfortable doing.
2. If you have a large syringe or turkey baster, you can give him a warm water enema. Obviously, this is not for the faint hearted. I would lubricate the end of the syringe or baster as I mentioned above, gently insert into his rectum about 1 inch and gently squeeze the warm water into him.
You will probably need to repeat this procedure several times to loosen up the hard stool that's in his colon.
Every step should be done gently so as not to hurt him.
3. You can give him an over the counter, human enema such as a single pediatric glycerin suppository. Several may need to be given before his colon is evacuated although you could give warm water enemas, too.
Oral laxative options:
1. Laxatone or Laxaire (or similar products) which are hairball laxatives for cats. These products will work very well on a smaller dog. They are available at pet or grain stores. You would give 1-3 inches 2-3 times a day.
2. Canned pumpkin (NOT the pie mix); ½ -1 tsp daily in food
3. Over the counter, human Miralax 1/4-1/2th tsp twice daily can work very well.
4. Oral Docusate Sodium (Colace) 25 mg once or twice a day for small dogs.
I suspect he may not be drinking or eating much at this point so dehydration may be a problem. I'd use a different syringe or small turkey baster to dribble human pedialyte into the side of his mouth to get fluids into him. Canned food can be mixed with the pedialyte in a blender until it's the consistency of soup which can also be dribbled into his mouth.
If you're not successful in getting him to produce a bowel movement with the above methods, then a vet visit may be prudent.
I hope this helps. Deb