Invented in the Year 281 and solely manufactured by Rejuvenation Corp, rejuve is the life-extending drug that is bought, distributed, and mandated by most human governments. Rejuve is a central part of life for most humans, the only race on which it works. Injected yearly, it leaves the subject sick for twelve hours, before causing them to cough up bloody phlegm. During this process, a few tens of thousands of calories are burned, foreign organisms (including most cancers) within the body die, and the aging process of the subject is slowed dramatically. Rejuve does not regrow destroyed organs or limbs, though often times this is overlooked given how dramatically it can repair damaged tissues.
What this means is that useful lifespans are extended by a significant amount, and many diseases becomes moderately expensive, but attainably solvable, problems. Trauma and old age are the primary killers among humans, with old age often being around one-hundred and one-hundred-thirty years old. Having the physical maturity level from age 20 or 21 (the earliest rejuve can safely be used) to age 50 or 51 doubled means that most humans are capable of both more working years and retirement years. Rejuve does not work any longer than thirty years.
This means that, during the longer fertile years, there is usually more help around from extended family members for current parents. This helps maintain the total population growth rate in the face of the many other distractions of interstellar life. This, coupled with the low cost of most resources necessary for life, is why humans usually maintain a better-than-replacement fertility, unlike the years of humanity being yoked under the United Nations hegemony.
The costs of rejuve are enormous, when the scope of its use is taken into account. Roughly 75% of the two and a half trillion humans use rejuve every year (with another two-hundred-fifty billion doses produced and sold for other purposes), and each dose costing NHD2.5; this may not sound like much, but the average human earns only NHD40. Rejuvenation Corp, not a publicly traded company, is estimated to have revenues in excess NHD5.5 trillion, making it the largest institution in human space–larger than any government, at least in terms of budget. Many people over the years have decried the power of Rejuvenation Corp, but every attempt to nationalize, take-over, seize, or infiltrate Rejuvenation Corp has run into the problem that the vats which produce the drug stop producing as soon as the system in which they are running is compromised. The company, however, tries to ameliorate these fears and concerns by maintaining a small security force, smaller even than many single-system polities, and relying on local police forces to preserve their property.