Clinical Features and Comparative Treatment Outcomes of Atomoxetine and Methylphenidate in Omani Adults with ADHD.

Objectives: To investigate the clinical presentation and treatment outcomes in Omani adults diagnosed with attention-deficit hyperactivity disorder (ADHD), with a focus on the efficacy of atomoxetine and methylphenidate in reducing symptoms, and identify clinical predictors of treatment response. Methods: This prospective study enrolled Omani adults with ADHD receiving treatment at Sultan Qaboos University Hospital, Oman. Data on sociodemographic and clinical history were collected. Treatment response was quantified using the Clinical Global Impressions-Improvement (CGI-I) scale, after three months of initiating treatment. Statistical analysis used independent chi-square tests and t-tests, with a significance threshold set at p < 0.05. Results: Among 171 participants, 60.8% were male. The majority (80.7%) received methylphenidate, while the others (19.3%) received atomoxetine. Inattentive subtype of ADHD (66.1%) was the most common, followed by combined hyperactivity and inattention (24.0%). Most (72.5%) patients had at least one comorbidity. After three months, 83.6% of the patients showed significant improvement on the Clinical Global Impressions-Improvement scale. Response rate for methylphenidate (84.8%) was higher than for atomoxetine (78.8%). Significant predictors of treatment response were male sex (odds ratio = 2.42, 95% CI: 1.00-5.71; p = 0.044) and absence of a family history of ADHD (odds ratio = 2.93, 95% CI: 1.18-7.28; p = 0.020). Conclusions: Both atomoxetine and methylphenidate were effective in treating adult ADHD, but methylphenidate showed a higher response rate. Male sex and the absence of a family history of ADHD were associated with greater response to treatment. These factors may serve as clinical indicators for tailoring pharmacological treatment decisions for individual adult ADHD patients in Oman.