Light is electromagnetic radiation that can be detected by the human eye. It is an energy form capable of damaging materials such as fibers, paintings/photographs, clothing, plants and drug products. The human eye can detect only wavelengths of light that make up the visible spectrum (color). Unseen components of the electromagnetic spectrum, such as ultraviolet & infrared can also severely affect objects.
Light: May the 5th Be With You… Wait, That’s Not Right?
Light & Light Sensitivity
Ultraviolet (UV) Light
UV has a wavelength of 10-380 nm. Wavelengths below 300 nm do not penetrate the earth's atmosphere and glass cuts out UV radiation with less than 320 nm.
The UV wavelengths of concern are 320-380 nm. This invisible UV radiation is highly energetic and causes photo-chemical deterioration. There is a high proportion of UV radiation in daylight and a significant amount emitted by fluorescent tubes.
Visible Light
Visible light (380-700nm) affects an object in two important ways - it can lead to its deterioration, and it can affect the way an observer perceives an object.
Deterioration is caused not only by high energy light at the blue end of the spectrum but also by heat produced by lower energy red light. Exposure to brighter, more intense light increases the rate at which light-induced damage occurs.
Infrared (IR) Light
IR radiation, with a wavelength of 770+nm, can cause objects to heat up and accelerate chemical deterioration processes. It is also capable of producing changes in humidity levels.
Under conditions of reduced relative humidity objects can become brittle, while increased relative humidity will increase corrosion of metals. Such changes in relative humidity correspond to the IR source being on and/or off.
Light Sensitivity
Light has many effects, the most noticeable of which are color changes induced in objects. Different materials react to light in different ways. Some materials fade while others darken. In addition to inducing color changes in objects, exposure to light is also responsible for weakening fibers of organic and inorganic material such as wood, textiles, or modern polymers (i.e., paint).
Lightsabers
Lightsabers are thought by many to tame what is called the fourth state of matter (after solid, liquid & gas), plasma – matter that is so hot that its component atoms fall apart to form a beam of positively and negatively charged cations & anions.
The force of the Jedi is the only known power in the universe able to contain the high instability and temperatures of plasma.
Light Sensitivity in Pharma
Exposure to light is a concern with numerous medications due to the potential for photodegradation or other chemical reactions during manufacturing, storage, and administration. This may result in potency loss, altered efficacy and adverse biological effects. The sensitivity of a drug to a distinct spectral region of light may vary with its chemical structure, photo-reactivity, and nature of the dosage form. The photochemical behavior of a drug provides guidance for handling, packaging, and labeling of drug products. Light sensitivity is very much like oxidation, whereby it affects AbbVie from the API manufacturing floor all the way to the final packaged drug product!
Stability
Light sensitivity is tested and evaluated as part of API and drug development. According to ICH Q1B (the universal guideline the pharma industry uses for light sensitivity), the intrinsic photostability characteristics of new substances and products should be evaluated to demonstrate that light exposure does not result in unacceptable change. Normally, photostability testing is carried out on a single batch of material.
Manufacturing
One way to protect light sensitive products during manufacturing is by controlling the environment such as using brown colored light (or UV-Free Lamps) during the manufacturing process. Brown light is longer in wavelength, making it less energetic and likely to cause product degradation. Another way is in the formulation itself by adding specific excipients that can counteract degradation.
Packaging
Tablets and pills made using direct compression containing light sensitive drugs should be packaged with a colored film to protect the product from light and prevent degradation. Usually, such tablets use alu-alu or amber blister packing to protect the light-sensitive drug. Another type of packaging for photo-sensitive drugs is glass vials/amber bottles. They inhibit the transmission of light with a wavelength shorter than 470 nm, thus reducing the photolytic degradation of the substances. Amber glassware is also used to make sample solutions for testing some products in our quality labs.
