What is Photopheresis?
Your doctor has recommended that you have Photopheresis treatment for your condition, but what is Photopheresis?
Firstly you can be reassured that Photopheresis is a safe therapy used to treat skin and other conditions where the white blood cells are thought to be the cause of the disease.
Photopheresis is en Extracorporeal Photoimmune Therapy and whilst this may sound complicated, broken down it is simple to understand.
- "Extracorporeal" means outside the body
- "Photo" means light
Photopheresis treatment primarily involves the patient being attached to a machine either by their central venous line if one is in place or, after having a needle inserted into one of the veins in their arm so that blood can temporarily be drawn from the body.
During treatment the patient's blood is drawn off and centrifuged. The red cells and portion of plasma cells not required are returned to the patient after each cycle whilst the amount of leukocytes or buffy coat and plasma required are isolated for further treatment. The whole process takes between one and three and a half hours depending on which machine is used. Information on both machines can be found on the Therakos Web site. With all treatments only a portion of blood is removed, about a pint, similar to that given when people are blood donors and on completion of the treatment, all blood will have been returned to the patient.
Once the leukocyte enriched blood is collected a drug called Uvadex (Methoxsalen) is added to make the T-Lymphocytes more sensitive to ultra violet light and so promote the death of the diseased cells The blood is then exposed to a prescribed amount of ultra violet light. The exact mechanism of the action of Uvadex is not known but the best known chemical reaction of Uvadex is with DNA.
When Uvadex is photoactivated it binds with the DNA of the nucleated cells to prevent further replications leading to a loss of cell viability over several days. After photoactivation the leukocyte enriched blood is returned to the patient. It is thought that these reinfused damaged cells generating an increase in the immune system activity, thus encouraging the production of healthy lymphocytes.
This leads to the question what is Uvadex:
Uvadex - Methoxsalen pronounced (METH-OX-A-LEN) belongs to a group of medicines known as Psoralens. It is a naturally occurring photoactive substance found in the seeds of the Ammi-Majus plant.
The exact mechanism of action of Uvadex is not quite known. The best bio-chemical reaction of Uvadex is with DNA, when photoactivated Uvadex forms bonds with DNA which leads to the formation of both mono functional (additional to a single strand of DNA) and bi-functional adducts (cross linking of psoralens to both strands of DNA).
Uvadex is used in conjunction with ultraviolet light to treat the white cell layer (Buffy Coat) from your blood in a process called photopheresis.
DOSAGE AND ADMINISTRATION
Uvadex is a sterile solution supplied in 10ml vials containing 200µg Methoxsalen (concentration of 20µg / ml). The dosage of Uvadex for each treatment is calculated based on the volume of buffy coat collected using the following formula. Treatment Volume Collected x O.O17=mls of Uvadex to be administered directly into recirculation bag.
EXAMPLE: - 240mls (Treatment Volume) x 0.017 = 4.08mls. 4.08mls should be rounded to the nearest 10th, e.g. 4.1mls of Uvadex administered under the supervision of doctor or health care worker.
Uvadex has an affinity to plastic and will lose its potency if it is left in a plastic syringe, so Uvadex should always be drawn into a syringe immediately prior to injection into the recirculation bag.
PRECAUTIONS BEFORE ADMINISTRATION OF UVADEX
Allergies
The doctor or nursing staff must be informed of any unusual or allergic reactions to Psoralens. Also any reactions to certain foods, dyes or preservatives.
Diet
Certain foods while receiving Uvadex treatment may increase skin sensitivity. Foods such as limes, figs, parsley, parsnips, mustard, carrots and celery should be avoided if possible whilst being treated.
Pregnancy
Studies in animals have found that Uvadex causes birth defects and death of the fetus. Pregnancy should be avoided whilst having treatment, but the doctor or nurse should be informed immediately if there is the possibility of positive pregnancy.
PRECAUTIONS AFTER EXPOSURE TO UVADEX
Uvadex is inert until exposed to UVA light. Once blood containing Uvadex is reinfused back strict precautions must be adhered to.
- Uvadex increases skin sensitivity and can cause premature aging of the skin, therefore a high factor sun block must be applied to exposed skin after treatment. Exposure to the direct sun or indirectly e.g. through window glass or even on a cloudy day could cause serious sunburn.
- Uvadex may cause cataracts in patients if exposed to large doses of UVA light so it is advisable to wear wrap around UVA protected sun glasses for 24 hours after treatment any time they are exposed to direct or in direct sunlight.
- If there is any history of basal cell carcinoma the patient should be strictly monitored as treatment with Uvadex can increase risks of skin cancer. Any skin sores that do not heal, new skin growths or skin growths that have changed in anyway should be advised to the doctor or nursing staff.
Treatment with Uvadex may cause a slight reddening of the skin 24 to 48 hours after each treatment has finished. This is normal and nothing to be alarmed about. However the doctor or nursing staff would need to be informed immediately should the skin become sore, blistered or peeling after treatment.
Conditions treated at Rotherham General Hospital include: -
- Cutaneous T-cell lymphoma (CTCL)
- Chronic graft versus host disease (GvHD)
- Systemic sclerosis
- Scleroderma