Impact of a Government Ban on Paraphenylenediamine (PPD) Availability: An Interrupted Time Series Analysis of Suicidal Poisoning Cases in Bahawalpur, Pakistan (2016–2024)

Paraphenylenediamine (PPD), locally known as “Kala Pathar”, has historically been a major agent of suicidal self poisoning in Southern Punjab, Pakistan. In response to escalating morbidity and mortality, the Government of Punjab implemented a policy prohibiting the commercial scale distribution of raw PPD at the end of 2017. This study aimed to quantitatively evaluate the impact of this policy on the incidence of PPD-related suicidal poisoning in Bahawalpur using an interrupted time series design. A quasi-experimental, retrospective interrupted time series (ITS) analysis was conducted using hospital records from the emergency department of Bahawal Victoria Hospital, Bahawalpur, from January 2016 to March 2024. Annual counts of confirmed PPD poisoning cases were analyzed. The intervention point was defined as January 2018. Segmented regression analysis was performed to estimate changes in both the level and the trend following policy implementation. A total of 4455 PPD poisoning cases were recorded during the study period. Prior to the intervention, cases increased from 832 in 2016 to a peak of 1243 in 2017. Following the prohibition, cases declined sharply to 407 in 2019 and further to 155 in 2023. Segmented regression analysis demonstrated a statistically significant immediate reduction in case level after the intervention (β2 < 0, p < 0.05), along with a significant negative change in post intervention trend (β3 < 0, p < 0.05), indicating a sustained decline in PPD poisoning incidence. The majority of cases occurred among males (72%) and individuals aged 21–40 years (48%). The prohibition of commercial scale PPD distribution was associated with a significant and sustained reduction in PPD-related suicidal poisoning in Bahawalpur. These findings support targeted means restriction policies as an effective suicide prevention strategy in resource limited settings.