Agonists produce significant, although mild, side effects including somnolence, hallucinations, insomnia, nausea, and constipation. Sometimes, side effects appear even at the minimal clinically efficacious dose, leading the physician to search for a different agonist or kind of drug. When compared with levodopa, while they delay motor complications, they control worse symptoms. Nevertheless, they are usually effective enough to manage symptoms in the initial years. They are also more expensive. Dyskinesias with dopamine agonists are rare in younger patients, but along other side effects, more common in older patients. All this has led to agonists being the preferential initial treatment for the former as opposed to levodopa in the latter. Agonists at higher doses have also been related to a wide variety of impulse-control disorders.