Amendments to the county’s social host ordinance that prescribe punishments for illegal drug use among minors at parties are poised to become law, following a first reading of the proposed changes that supervisors will vote on next Tuesday. 

Passed in 2006, the ordinance previously only prohibited adults at parties from serving alcohol to kids, and imposed fines for violations. The new amendments would add underage possession and consumption of controlled substances—including marijuana and prescription pills—and would sentence underage offenders to community service through a restorative justice program. 

It would not apply to those who have valid prescriptions for their medications, or to those who have recommendations or I.D. cards for medical marijuana.

The updated ordinance would fine adult hosts $750 for the first offense, $1,500 for the second and $2,500 for the third. Since 2007, the ordinance has resulted in 48 citations; slightly less than half of those violators paid $750 fines, while those with limited incomes were given the option to participate in community service.

The changes come amid growing concern over pill abuse in Marin, where county public health officials have estimated one in five high school students uses prescription narcotics recreationally. Likewise, marijuana use remains high, and some local youth activists are viewing the amendments as a step toward preparing for the possible legalization of marijuana in California. 

“I think that the county is trying to take a public health approach to the use of marijuana in Marin,” said Madeline Hope, the director of the Tomales Bay Youth Center. “It’s going to come onto the ballot, and it’s something we have to be ready to grapple with.”

Ms. Hope pointed to the public-health attitude toward marijuana adopted by the Los Angeles County Department of Public Health, which issued a memo last October calling on local governments and community leaders to “coordinate their efforts to effectively expand and exercise their authority to set a public health framework for the current and future consumption of marijuana.” 

Such a framework, Ms. Hope said, helps county public health officials create more consistent messaging about what is and is not tolerated on the subject of marijuana consumption.

According to the 2013-14 California Healthy Kids Survey, which compiles student-submitted data on drug and alcohol use, 31 percent of Marin’s 11th graders smoked marijuana over a month’s time. More troubling is the 16-percent tally of 11th graders taking prescription pills, which county officials have said are causing an “epidemic” of overdoses among kids and adults alike. 

In 2013, pill abuse contributed to 27 accidental fatal drug overdoses in Marin, according to the county’s public health officer, Matt Willis.

Meanwhile, law enforcement officials are hoping the amendments will curb the popularity of what they call “pill parties,” in which several kinds of prescription pills, often raided from a parent’s medicine cabinet, are poured randomly into a bowl at a party, or even at school.

Like county officials, Don Carney, who founded and runs the Y.M.C.A. Youth Court, which employs restorative justice principles, has seen a rise in pill abuse among minors in recent years. Substance-driven infractions account for around 80 percent of the cases brought before the court. 

Mr. Carney placed blame on affluence, which makes it easier for kids to obtain drugs like oxycontin and percocet, as well as the power of large pharmaceutical companies to produce and market these drugs in massive quantities. And while he criticized many parents for putting too much pressure on children to succeed in school, he also blasted some parents for not being enough of a presence in their kids’ lives.

For Mr. Carney, the real benefit of the amendments would be the requirement that underage violators participate in a restorative justice program like the youth court. To date, about 95 percent of the nearly 1,000 kids who have gone through the court complete their sentences, with only eight percent recidivism the following year.

For her part, Ms. Hope attributed a lack of knowledge around how local kids are using pills to the rural nature of West Marin, which she said has a higher rate of marijuana smoking than anything else. And it becomes even more difficult to track their habits, Ms. Hope said, once middle school students enroll in more affluent school districts over the hill.

“Kids aren’t necessarily speaking about it with adults,” Ms. Hope said. “I think it’s something that they’re still just learning about. It’s hard to know what the impact is.”