Michael Law

Michael Law

Professor, School of Population and Public Health, University of British Columbia
Director, UBC Centre for Health Services and Policy Research, University of British Columbia
Canada Research Chair in Access to Medicines

Dissertation Title:  "Longitudinal Methods for Investigating Pharmaceutical Advertising, Adherence and Prior Authorization Policies"

In this dissertation, I use longitudinal methods to investigate three pharmaceutical policy topics.

The first paper examines the impact of direct-to-consumer advertising (DTCA) for four heavily marketed medications using a controlled, longitudinal time series design. We studied Canada — where there is substantial cross-border exposure to English US DCTA — and compared prescribing rate differences between predominantly English- and French-speaking provinces. The prescribing rate difference for three drugs (mometasone, tadalafil and zopiclone) did not increase after DTCA. In contrast, tegaserod prescriptions increased 42% in English-speaking provinces, but this effect did not persist over time. These findings suggest that DTCA campaigns may be relatively ineffective at increasing prescribing rates, but may be influential when drugs have advantages relative to existing therapies. My second and third papers investigate atypical antipsychotic agents, a widely-used treatment for serious mental illnesses, including schizophrenia and bipolar disorder.

The second paper investigates the temporal relationship between medication nonadherence and hospitalization risk for individuals with schizophrenia. We used a daily measure of medication availability and found individuals in the first 10 days following a missed prescription refill had an over 50% increase in hazard of mental health hospitalization and 77% increase in hazard of schizophrenia-specific hospitalization. Similarly, medication gaps of more than 30 days were associated with 50% increased hazard of hospitalization. These findings suggest clinicians and Medicaid programs might use pharmacy claims to target future adherence interventions.

Finally, the third paper examines the impact of Medicaid prior authorization programs for atypical antipsychotic agents, which have been implemented to reduce costs in more than 10 States. We used interrupted time series analysis to study the impact on market share of non-preferred agents and costs in West Virginia and Texas. These policies reduced market share for non-preferred agents by 14% in West Virginia and 3% in Texas. However, prior authorization did not decrease pharmacy reimbursements in either state. Further evaluation of the clinical consequences resulting from such policies is urgently needed to determine whether their potential clinical risks outweigh their limited cost impact.


Graduation Year

Dissertation Committee Member