Purpose: To describe nationwide dispensing patterns of methylphenidate in Australia before and during recent prolonged supply shortages, and to assess the extent to which Section 19A (S19A) overseas substitutes contributed to population-level utilisation during the shortage period. Secondary aims were to compare methylphenidate dispensing with other ADHD medicines, examine changes in dispensing across individual strengths and formulations, and quantify delays between S19A approval and Pharmaceutical Benefits Scheme (PBS) listing. Methods: A population-based cohort study was conducted using publicly available monthly dispensing data from the Pharmaceutical Benefits Scheme (PBS) and Repatriation PBS (January 2020–October 2025). Data were standardised to dispensings and Defined Daily Doses (DDD) per 100,000 population. Methylphenidate shortages were identified using the Therapeutic Goods Administration Medicines Shortages database. S19A approvals, PBS listing dates and lapse dates were obtained from the S19A approvals database to determine delays to subsidised access. Results: Dispensing of ADHD medicines increased substantially from 2020 to 2025. Methylphenidate dispensing increased overall but plateaued from late 2024 onward, coinciding with widespread supply disruptions affecting multiple strengths and formulations. DDD analysis demonstrated abrupt reductions in extended‑release methylphenidate strengths (particularly 36 mg and 54 mg) during shortages, with partial compensatory increases in other strengths. Fifteen overseas-registered methylphenidate products received S19A approval; however, time to PBS listing ranged from 83–166 days (median 162 days). After PBS listing, S19A products contributed to <1.5% of all methylphenidate dispensings between July–October 2025. Conclusion: Methylphenidate dispensing in Australia became unstable during extensive supply shortages from late 2024, with incomplete substitution across strengths and modest increases in alternative ADHD medicines. Although numerous S19A products were approved, there was minimal uptake of these products at the population level. As ADHD medicine utilisation continues to rise, strengthened national strategies to improve supply chain resilience, transparency and responsiveness are needed.