Injecting drugs through the skin
Advances in drug delivery has seen a move from intravenous adminstration of drugs towards subcutaneous delivery.
INNOVATION in medicine has advanced in many ways.
Personalised medicine, precision medicine, immunotherapy, digital healthcare – these are some of the advances that many of us have heard about recently.
Another area that we are seeing innovation is in the administration of drugs.
Parenteral drug delivery involves introducing drugs into the body via needle injection through the skin.
The intravenous and subcutaneous routes are the two more common types of injection.
Others include intradermal ( just below the skin), intra- muscular ( into the muscles) and intrathecal ( into the spinal canal).
Intravenous route
Intravenous injection (IV) delivers the drug directly via the vein into the systemic blood circulation.
Using this method, we have better control over the drug delivery in terms of the rate and amount administered.
At the same time, it helps to avoid all the vagaries encountered via other routes.
Another advantage is that very rapid response can be achieved via IV injection.
However, the administration requires skilled personnel and the product has to ful- fil extra formulation requirements. Not only has the product to be sterile, it must be particulate free, iso- osmotic (similar osmotic pressure to the blood) and has a suitable pH to avoid damaging the blood vessels.
Hence, IV injection carries higher and more risk, compared to that of the subcutaneous (SC) route.
Subcutaneous route
In comparison, SC injection is safer, less painful and more popular, especially when self- administration is required.
This type of injection is used when other methods of administration might be less effective.
For example, some medications can’t be given by mouth because acid and enzymes in the stomach would destroy or degrade them.
Basically, the injection is directed into the subcutaneous or fat layer beneath the skin.
SC injection has the advantage of a more prolonged duration of drug response.
The subcutaneous tissue has fewer sensory receptors than the skin.
Therefore, once the needle has penetrated the skin, further penetration of the needle into the subcutaneous tissue is relatively painless.
SC injections are administered at the upper arms, anterior ( front) or lateral ( side) areas of the thigh and the lower abdomen.
Diabetics on insulin therapy and rheumatoid arthritis patients are taught to selfadminister using this route.
Some pain medications like morphine and hydromorphone, as well as drugs that prevent nausea and vomiting like metoclopramide or dexamethasone, can also be given via SC injection.
Benefits of the subcutaneous route
Lately, there is a growing interest in SC injection as a preferred alternative not only to the oral route, but also for delivery of drugs that are con- ventionally given via IV.
For example, in palliative care, the SC route is recommended when patients are unable to swallow or experience nausea and vomiting.
Many compounds that were previously given via the IV route are now reformulated for SC injection.
This is especially useful for patients requiring long term treatment, such as those having chronic inflammatory conditions like rheumatoid arthritis.
Some cancer adjuvant treatments, such as monoclonal antibodies, have evolved from IV to SC injections.
It is also the preferred route for a new class of drugs in the form of peptides, which are not amenable for oral delivery.
From a patient’s perspective, switching from IV to SC injection is expected to improve quality of life, and for some, better adherence to treatment.
Firstly, patients would experience less discomfort related to IV injection, which uses a longer needle.
In those with veins that are difficult to access, it would mean significantly less pain from multiple attempts to access their veins.
As SC drugs can be selfadministered by the patient at home, patients no longer need to travel to the hospital and spend a significant amount of waiting and infusion time at the facility.
This is especially meaningful to patients who live in rural or distant areas from the nearest treatment facility and patients who are actively working and may need to compromise on work productivity to seek treatment during typical work hours.
Both of these factors, would lead to better patient experience in treatment and improve the compliance to treatment, compared to conventional IV treatment. Prof Yuen Kah Hay is an Honorary Professor at the School of Pharmaceutical Sciences, Universiti Sains Malaysia. This article is courtesy of Roche Malaysia.