Tiny sensor makes drug pumps safer
could improve the efficacy of pumps used to deliver drugs from
implanted reservoirs, according to one of the scientists behind the
project.
Liv Furuberg, of the Micro and Nanotechnology Laboratory in Oslo, Norway, told In-Pharmatechnologist.com that the new device is a flow metre - with fluid channels thinner than a strand of hair - which can help control the dosing of medicine.
The principle is not revolutionary - similar sensors are already being mass produced for use in accelerometers and tyre pressure sensors in cars - but it has not yet been applied in the medical device/drug delivery sector.
The active components in the sensor - which measures a change in pressure across the diameter of a microtube only a few thousandths of a millimetre thick - can measure liquid amounts of less than one-millionth of a litre. It combines the micromachined tube with electronics that are coated to allow them to be used in a liquid environment.
"Previous micromachined, pressure based, flow sensors could not allow liquid flow on both sides of one pressure membrane due to short-circuiting of the measurement bridge, said Furuberg.
The invention could mean safer dosing for patients reliant on a continual supply of medicine from medicine pumps, such as patients with cerebral palsy. Pumps used today for treating cerebral palsy deliver tiny, constant doses of muscle relaxants from a reservoir next to the spinal column. This avoids the massive doses - and accompanying toxicity - that are seen with oral dosing.
The implants have a pre-programmed refill time, with the reservoir needing to be topped up via an injection, typically every four months or so. However, current products do not actually measure the flow out of the reservoir, and episodes of unexpected empty reservoirs, resulting in severe muscle spasms, have been reported, according to Furuberg.
The flow sensor is manufactured by Norwegian company SensoNor, which recently became part of German electronics company Infineon Technologies.
Other potential applications for the sensor include portable morphine pumps for pain relief in cancer patients, as well as in diabetic patients who could have a medicine pump installed for round-the-clock insulin dosing.
A typical implantable drug pump can cost around €50,000, and the sensor would add only €10-€20 to the total, said Furuberg. SensoNor has already started talking with medical device companies about adding the sensor to some products, she said.
