Lower Drug Costs Now Act of 2019 This bill establishes several programs and requirements relating to the prices of prescription drugs. In particular, the bill requires the Centers for Medicare & Medicaid Services (CMS) to negotiate prices for certain drugs (current law prohibits the CMS from doing so). Specifically, the CMS must negotiate maximum prices for (1) insulin products; and (2) at least 25 single source, brand name drugs that do not have generic competition and that are among the 125 drugs that account for the greatest national spending or the 125 drugs that account for the greatest spending under the Medicare prescription drug benefit and Medicare Advantage (MA). The negotiated prices must be offered under Medicare and MA, and may also be offered under private health insurance unless the insurer opts out. The negotiated maximum price may not exceed (1) 120% of the average price in Australia, Canada, France, Germany, Japan, and the United Kingdom; or (2) if such information is not available, 85% of the U.S. average manufacturer price. Drug manufacturers that fail to comply with the bill's negotiation requirements are subject to civil and tax penalties. The bill also makes a series of additional changes to Medicare prescription drug coverage and pricing. Among other things, the bill (1) requires drug manufacturers to issue rebates to the CMS for covered drugs that cost $100 or more and for which the average manufacturer price increases faster than inflation; and (2) reduces the annual out-of-pocket spending threshold, and eliminates beneficiary cost-sharing above this threshold, under the Medicare prescription drug benefit.