Coolmine House, a voluntary organisation which has worked with addicts since 1973, says parents who want to protect their children from drugs must be prepared to "get in the way" even if it angers the children.
The group has recently organised a new course, the Parent-to-Parent Drug Prevention Workshop, to encourage parents to notice changes in their children's behaviour which might be linked with drug use.
"There is no place or village around the country where there are no drugs available," says Ms Marie Byrne, national co-ordinator for the course.
According to course facilitator Ms Maureen O'Connor, changes to look out for could include:
The child begins to mix with people whom the parent regards as undesirable.
A good student loses all interest in homework.
A child who was always particular about clothes stops paying any attention to how he or she dresses.
A child begins to sleep very late in the day.
A child expresses the view that he or she could handle drugs without being damaged by them. Parents must have the courage to make a stand in their children's interest, says Ms Byrne. "Sometimes you have to love them enough to be strict around certain areas," she says, "such as saying you can't go to that party because there are drugs and alcohol there."
Parents are afraid to ask their children about drugs in case they look foolish or upset the child. But the message of the course, she says, is: if they get upset, so what?
People who use drugs should not be let into the house, she says, and parents should insist on knowing where their children are.
What if the child threatens to leave home? "When a child says I am getting out, say `Will I pack your bags now or in the morning?'," says Ms O'Connor. And what if the child really goes and gets into serious trouble? Just because a child is at home does not mean he or she is safe, she insists.
"I know at least three young people who committed suicide in their own homes because they couldn't get money for drugs.
"The child will say `you don't trust me'," adds Ms Byrne. "The answer is trust is not given out free, it's earned.
"The parents want to be their child's friend - but you can't be their friend because their friends don't mind them staying out all night," she says. "You have to be their parent."
Even areas which don't see themselves as having a drug problem can benefit from the course, says Mr Brendan O'Sullivan, a course facilitator in Co Monaghan.
"We are parenting in a drugs age," says Mr O'Sullivan. Educating parents and families about drugs is one of the most effective ways of preventing a drugs problem from taking hold in an area, he says.
Coolmine charges £240 per week for each group taking the course, regardless of the number in the group. The cost is often subsidised by schools or other sponsoring bodies. The number of people in a group ranges from 12 to 35.
People interested in doing the course or in getting information on the issues mentioned here can contact Ms Byrne at Coolmine House, Lord Edward Street, Dublin 2.