Thursday September 3 2009
The majority of prescriptions were for children 14 years or older
“The number of children on anti-obesity drugs has risen 15-fold in the last 10 years”, The Daily Telegraph reported. It said that a study of data from GPs between 1999 and 2006 shows up to 1,300 children and teenagers a year could be prescribed the drugs, even though they are not licensed for use by children. The newspaper said that most prescriptions “were for 14-year-olds, although 25 prescriptions were written for children under the age of 12”.
This research looked at a selection of GP records from practices covering 5% of the population. It is a well-conducted study and the results are likely to be representative of the rest of the UK. It found that the prescribing of unlicensed anti-obesity drugs to children and adolescents has increased significantly in the past eight years.
Because the data were collected from the time just after orlistat was licensed in the UK, and before sibutramaine was available, it is not surprising that the increase has been so large. However, the estimated absolute number of prescriptions for adolescents (1,300 a year) is large and is another reminder of the growing obesity crises in the UK.
Where did the story come from?
This research was carried out by Dr Russell Viner and colleagues from the UCL Institute of Child Health and the University of London. The study was funded from various sources including the Higher Education Funding Council, the NHS, the National Institute of Medical Research and the School of Pharmacy at University College London.
The study has been peer-reviewed and approved for publication in the British Journal of Clinical Pharmacology.
What kind of scientific study was this?
The researchers that say the efficacy and safety of anti-obesity drugs (orlistat, sibutramine and rimonabant) have been poorly studied in children and adolescents. These drugs are commonly used in adults but are not licensed for children and, as such, prescriptions to children are being made off-label (otherwise known as unapproved use) by GPs, often on the authority of specialists.
Orlistat has been licensed for adults since 1998, sibutramine since 2001 and rimonabant since 2006. In 2005, the cost to the NHS of supplying two drugs, orlistat and sibutramine in England was £38.2 million. The US has different licensing arrangements to the UK. For example, orlistat is licensed in the US for patients over 12 years old. All countries recommend that diet and physical activity approaches be tried first before prescribing these drugs.
In this registry study, the researchers looked at the prescribing data from the UK General Practice Research Database. This holds anonymous prescribing details of patient consultations in GP surgeries covering 5% of the population.
Records from January 1999 to December 2006 were used to calculate the annual rates of anti-obesity drug use in each age and sex grouping (age-sex-specific annual prevalence). Prevalence was defined as the number of subjects with at least one anti-obesity drug prescription during the year of investigation, divided by the total number of patient years in the same year for that age.
There was only one prescription for rimonabant (in a patient aged 18 years in 2006), so the researchers only analysed the data for orlistat (78.4% of all prescriptions) and sibutramine (21.6%).
What were the results of the study?
The researchers say that 452 subjects received 1,334 prescriptions between January 1999 and December 2006.
The annual prevalence of anti-obesity drug prescriptions rose significantly from 0.006 per 1,000 in 1999 to 0.091 per 1,000 in 2006 with similar increases seen in both genders. This represents a 15-fold increase.
The majority of prescriptions were for children aged 14 years or older, although 25 prescriptions were made for children younger than 12 years.
Among the patients prescribed orlistat, 45% stopped after only one month and 25% of those prescribed sibutramine stopped within a month. The average duration of treatment was three months for orlistat and four months for sibutramine.
What interpretations did the researchers draw from these results?
The researchers say that the “prescribing of unlicensed anti-obesity drugs in children and adolescents has dramatically increased in the past eight years”. They say that the adolescents stopped taking the drugs before a weight benefit could be noted and that this suggests the drugs are “poorly tolerated or poorly efficacious when used in the general population.” They call for further research.
What does the NHS Knowledge Service make of this study?
The researchers acknowledge the epidemic of child and adolescent obesity in the UK and say that those who are already obese currently make up 7-10% of the child and adolescent population under 20 years old. This is clearly a problem that needs to be addressed. As a descriptive study, this research sought to identify and describe the problem and not to suggest specific answers.
The study has several strengths:
- As a population-based study, the estimates of prevalence are likely to be sound and as the people in the database are considered representative of the general population, it can be assumed that similar rates apply to the rest of UK primary care.
- The quality of the data collected in this database has been separately validated as accurate.
The researchers note that they were unable to include in their analysis any anti-obesity drugs prescribed from hospitals or any data on socioeconomic status or ethnicity. The impact of these on prescribing patterns would have added value to the study. The reasons for why the children stopped taking the drugs were not recorded either.
Overall, the 15-fold increase in prescribing does sound impressive. The actual increase was from six persons per million per year in 1999 to 91 per million in 2006. It is also perhaps not surprising that orlistat was so rarely prescribed in young people only a year after it was first licensed.