Every medical device is labeled with an expiry date that is supported by shelf-life data. Shelf life is the time period during which a medical device remains suitable for the intended use. An expiration date mentioned over the labels is the termination of shelf life, after which a percentage of the medical devices, may no longer function as its intended use.
To determine if a particular device requires a shelf life and assign an expiry date, there are a number of different parameters that must be considered based on the intended use of device, type of the device, Chemical, Physical, microbiological, toxicological, therapeutic as well as packaging aspects.
Shelf life is determined or estimated using two types of stability studies:
- Accelerated stability studies.
- Real-time stability studies
Accelerated stability studies is used to predict a medical device expiration date or life period in short span of time when there is no real-time data available.
The fundamentals of accelerated stability testing is based on the Arrhenius equation that describes relationship between storage temperatures and degradation rate:
lnK= lnA + Δ𝐸/𝑅𝑇
where K = degradation rate/s,
A = frequency factor/s, (Specifically relates to the molecular collision, deals with the frequency of molecules that collide in the correct orientation and with enough energy to initiate a reaction. It is a factor that is determined experimentally, as it varies with different reactions)
ΔE = activation energy (kJ/mol),
R = universal gas constant (0.00831kJ/mol),
T=absolute temperature (K)
A real-time stability study is conducted to determine long term product stability. This is carried out for a longer duration of the time period to allow greater degradation of the product under specified storage conditions.
For Active medical device the lifetime of the medical device is considered and it is calculated by compiled calculation of all the critical components of the device.