Niels Skipper

Determinants of generic vs. brand drug choice: evidence from population-wide Danish data.

We investigate if demand for branded prescription medications in post-patent markets is patient- or doctor driven. When drugs go off-patent the brand medication often maintains non-negligible market shares. We use population-wide Danish data including all prescriptions for seven blockbuster drugs from 1998 to 2008, which amounts to 13,415,012 prescriptions. At the outset, descriptive statistics suggest large variation in drug choice over doctors. Nonetheless, using a two-way fixed effects model we find that the primary determinants of brand drug use are unobserved patient characteristics and price effects.

ON THE DEMAND FOR PRESCRIPTION DRUGS: HETEROGENEITY IN PRICE RESPONSES

This paper estimates the price elasticity of demand for prescription drugs using an exogenous shift in consumer co-payment caused by a reform in the Danish subsidy scheme for the general public. Using purchasing records for the entire Danish population, I show that the average price response for the most commonly used drug yields demand elasticities in the range of -0.36 to -0.5. The reform is shown to affect women, the elderly, and immigrants the most. Furthermore, this paper shows significant heterogeneity in the price response over different types of antibiotics, suggesting that the price elasticity of demand varies considerably even across relatively similar drugs.

INCOME AND THE USE OF PRESCRIPTION DRUGS FOR NEAR RETIREMENT INDIVIDUALS

Understanding how demand for prescription drugs responds to changes in income is important for assessing the welfare consequences of reforms affecting income. This becomes more imminent as age progresses, because the use of prescription drugs and the associated budgetary burden increases dramatically from about age 55. In this paper we estimate how demand for prescription drugs varies with income for a sample of near retirement individuals. Estimating the prescription drug demand response to income changes is complicated because an important explanatory variable, the health capital, is unobserved, and because demand is potentially dynamic, for example because some drugs are habitual. The analysis is based on a novel panel data set with information about purchase of prescription drug demand for a very large number of Danish individuals over the period 1995-2003. Our preferred model that takes into account the aforementioned complications performs better in an external validation test than models that can be estimated on cross section data. Results indicate that demand does respond to variations in income and that reforms affecting income therefore will affect the use of prescription drugs.

On reimbursement reforms and stockpiling of prescription drugs: The case of insulin

OBJECTIVES To show that care should be taken in studies which aim at linking prescription drug prices to purchased quantities due to anticipation and stockpiling effects. METHODS Using purchasing records for a 20% random sample of the entire Danish population, the effects of increasing co-payments are estimated using fixed effects techniques. RESULTS The results indicate that insulin-takers react to announced changes in reimbursement policies by stockpiling on their medications. CONCLUSION Using before-and-after comparisons to identify the price responsiveness of prescription drug demand can be very misleading, when changes in co-payments are announced.

On Utilization and Stockpiling of Prescription Drugs When Co-Payments Increase: Heterogeneity Across Types of Drugs

This paper investigates prescription drug utilization changes following an exogenous shift in consumer co-payment caused by a reform in the Danish subsidy scheme for the general public. Two different types of medication are considered – insulin for treatment of the chronic condition diabetes and penicillin for treatment of non-chronic conditions. Using purchasing records for a 20% random sample of the Danish population, I show that increasing co-payments lower the utilization of both drugs. I demonstrate that individuals treated with drugs for chronic conditions react to the policy change by stockpiling on their medications. This has implications for other papers in the literature that use variation in subsidy rates over time to estimate the price elasticity of demand. This is not the case for penicillin however, where price elasticities are estimated to be in the -.18 – -.35 range. Further, I find that the lower part of the income distribution is more price responsive.

Physicians are more likely than non-physicians to use brand-name drugs to treat their chronic conditions

Background Little is known about the treatments physicians choose for themselves compared with how they treat their patients. We determine if physicians prescribe different treatments to patients than to themselves. Methods Population-based cohort study from 2004 to 2012 examining prescription claims of all Danish primary care physicians (PCP; n=3088) and all other Danish adults (n=2 334 590) who received a first-time prescription from a PCP for a statin (n=455 586), calcium channel blocker (CCB, n=330 369), serotonin-norepinephrine/selective serotonin reuptake inhibitors (SN/SSRIs, n=423 740), proton pump inhibitor (PPI, n=671 965) or antihistamine (n=456 018). The main outcome is the brand-name or generic status of the first prescribed drug. A logistic regression model compared outcomes, unadjusted and adjusted for sociodemographic characteristics and coverage information. Results For drugs that require chronic treatment (statins, CCBs, SN/SSRIs), the relative risk (RR) for PCPs (PCP patients) being treated with a brand drug was 3.86 (95% CI 3.33 to 4.47; p<0.001). This difference remained significant when adjusting for covariates (adjusted RR=2.51 (95% CI 2.16 to 2.92; p<0.001)). For non-chronic drugs (PPIs, antihistamines), the RR for PCP patients was (RR=1.13 (95% CI 1.08 to 1.20; p<0.001)), and this difference was explained by higher income. Physicians are not more likely than non-physicians, however, to be treated with brand-name versions of drugs that are available as generics. Conclusion Physicians are more likely than non-physicians to be treated with brand-name drugs without generic equivalents in three chronic treatment drug classes but not in two acute treatment drug classes. Guidelines can lead to lower brand-name drug use than physicians prefer for themselves.

INCOME AND THE USE OF PRESCRIPTION DRUGS FOR NEAR RETIREMENT INDIVIDUALS: INCOME AND THE USE OF PRESCRIPTION DRUGS

In this paper, we estimate how demand for prescription drugs varies with income for a sample of near retirement individuals. The analysis is based on a novel panel data set with information about the purchase of prescription drugs for a large number of Danish individuals over the period 1995-2003. Our preferred model performs better in an external validation test than models that can be estimated on cross section data. Results indicate that demand does respond to variations in income and that reforms affecting income will therefore affect the use of prescription drugs.