And the alarming consequence of this is that adults often decant pills into non-safe containers, a practice thought to contribute to around 10,000 cases of accidental poisoning each year in the UK, 80 per cent of which involve children under four.
A study conducted by Belinda Winder and colleagues at the department of mechanical engineering at Sheffield University in the UK, conducted a survey to gauge the extent of the problems adult have with child-resistant closures (CRCs).
The project involved a diary study with 250 consumers and then a questionnaire with 100 volunteers aged 20 to 84. Not only did 90 per cent of those involved in the latter study report difficulties opening CRCs, but the evidence suggests that by the age of 50 the average person can expect to have frequent problems opening this type of packaging.
Worryingly, respondents in the survey reported considerable difficulties with the standard 'push down and twist' or 'squeeze and twist' pill bottle closures, mainly because they rely on physical strength to open. In many cases, patients taking the pills may lack the strength or dexterity to open these bottles, according to Winder.
Cognitive, not physical barrier
A psychologist by training, Winder has been instrumental in developing a new concept for CRCs based on a cognitive barrier to opening. In other words, packs should require a couple of physically undemanding actions that can be taught to an adult but are too sophisticated for a child to work out.
Winder has collaborated with a UK design company called Factory Design to come up with various CRC concepts that fulfil this cognitive barrier function.For example, one design - known as the slide - requires the patient to align three separate sliding tabs in a given pattern before the pack will open.
But physical limitations other than strength can be used. For example, Winder and Factory Design have developed another CRC called the Poke, which requires a finger to be inserted deep into a device to push a button which opens the pack. A child's finger would be too short to manage this.
In fact, up to 90 per cent of adults struggle to open child-proof packaging, according to a report in the journal of the Engineering and Physical Sciences Research Council.
The packaging concepts are now available for licence from the Faraday Packaging Partnership, an R&D network centred on the Universities of Leeds, Sheffield and York and Pira International.
Meanwhile, a similar project has been undertaken by the UK's Child Safety Packaging Group, which has designed a series of child-resistant flexible packaging.
Speaking to In-Pharmatechnologist.com at the TOTAL exhibition last month, the CSPG's Stephen Wilkins noted that the group has commissioned a number of new package designs that try to improve the design of pharmaceutical packs, and is offering the intellectual property behind them free to any organisation interested in developing them. He presented a few examples at TOTAL, including a blister that can only be opened by squeezing the pack with an adult-sized hand.