According to the American Society for the Prevention of Cruelty to Animals (ASPCA), veterinarian-approved laxatives or stool softeners, such as Metamucil, are both ways to treat constipation in dogs. Dogs can eat bran cereal or canned pumpkin for occasional constipation.
Constipation occurs in dogs for a number of reasons. According to WebMD, lack of water is a common cause of constipation. Increasing a dog's water intake helps alleviate constipation problems. Another way to help with constipation is through a balanced diet. Dogs that eat poorly often suffer from constipation, while dogs that eat a diet with the right amount of fiber and other nutrients are less likely to have constipation problems.