Bupropion reduces the severity of nicotine cravings and withdrawal symptoms. Nicotine replacement therapy works by reducing cravings caused by nicotine addiction. Chronic dieters constantly work at resisting their cravings and limiting their food intake. Studies have shown that alcohol dependence relates directly to cravings and irritability. The medication bromocriptine can reduce cravings and withdrawal symptoms within 24 hours. A review reported that extended calorie restriction suppresses overall and specific food cravings. One of the treatments for morning sickness consists of accommodating food cravings and aversions. Buprenorphine and methadone can help decrease drug cravings. Recent research has shown diltiazem may reduce cocaine cravings in drug-addicted rats. To a recovering heroin addict, the synthetic opiate gives rise to strong cravings. Food cravings and impotence have also been reported. "Dukkha" may mean disappointment, desires, cravings, bereavement, unfulfillment, or dissatisfaction. Medications are a useful aid in helping to prevent or reducing drug cravings. Different cultures have different popular pregnancy cravings. Further research is being conducted to determine the mechanism behind food cravings during pregnancy.