Methods and compositions are provided for preventing or reversing loss of the therapeutic effect of a drug, where the loss is associated with the repeated administration of the drug to a patient. The method includes administering to the patient a dopamine receptor agonist or partial agonist or a drug that increases the extracellular level of dopamine by enhancing release of dopamine, decreasing the removal of dopamine from the extracellular space, enhancing the synthesis of dopamine within the brain, or decreasing metabolic degradation of dopamine and also administering to the patient an opioid receptor antagonist in an ultra-low dose amount, wherein the ultra-low dose amount is effective to prevent or reverse loss of therapeutic effects associated with the repeated administration of the drug to the patient. The methods are useful for various treatments, including treating Parkinsons Disease, Restless Leg Syndrome, depression, schizophrenia, psychostimulant drug abuse, or attention deficit disorder.
