Delivering drugs through the skin
When it comes to a medicine’s route of administration, there are some people who might find it difficult to swallow a tablet or capsule, and/or who are frightened of needles or injections.

Fortunately, some medicines can be formulated to be administered in the form of a transdermal patch.

Transdermal patches are a well-established method of drug delivery that use the skin as the site of administration.

They act as a carrier for a specific, predetermined dose of the drug, holding it until it is applied to the skin.

Transdermal patches have an adhesive that secure it to the skin.

This is important as they need to stick to the skin in order to deliver the drug.

Once the patch has adhered to the skin, the medicine contained within will begin to be absorbed by the skin and permeate into the bloodstream in gradual quantities over a regular and specified period of time.

The medicine absorbed then circulates through the body and is distributed to the site it is intended to affect.

The patch will continue to release its active ingredient until it is either fully absorbed or the patch is removed.

The length of use and the amount of medicine delivered can differ from patch to patch.

As can be seen, transdermal patches offer a number of benefits to patients, including steady and regular absorption of the medicine, a non-invasive administration method that involves minimal pain and burden to the patient, an easy method of application, and the potential to reduce the frequency of administration.

They can be used to deliver a range of medicines into the body.

Some commonly-used transdermal patches include those used for pain management, contraception, nicotine replacement therapy (to help with quitting smoking) and hormone replacement therapy.

Putting on the patch

Here are some important points to take note of when applying and removing a transdermal patch:

> Gather as much information as possible

The first step to take when applying a transdermal patch is to read the label or product leaflet.

This is important to ensure that you use the patch in the correct way.

Several important pieces of information are usually stated on the label or product leaflet, such as the active ingredient, specific instructions for use, and expiration date.

Ensure that the patch contains the correct medicine to provide the intended effects and is within its usable period (i.e. not expired).

> Select the appropriate body area

The most appropriate body areas for patch application are those with flat surfaces, such as the chest, back, flank or upper arm.

You may refer to a doctor, pharmacist or the package insert to determine which area is suitable for your particular patch.

For instance, certain patches should be applied to the upper chest, or an upper, outer arm.

Meanwhile, others should be placed on the lower abdomen or hip.

It is best to avoid hairy areas, if possible.

If it cannot be avoided, then the hair should be clipped or carefully trimmed using scissors.

Shaving the area is not advisable, as it may irritate the skin.

If the only area available is a recently-shaved one, then patients need to wait at least three days after shaving before applying the patch.

For certain groups of patients, such as young children, the patch can be applied to their back so that they cannot remove it.

> Be hygienic while preparing to apply the patch

If there is a need to clean the application site, use only clear water and let the skin dry completely.

Make sure the skin is clean and free of any powders, oils or lotions.

It is also important for patients to wash their hands with water and soap before and after each application.

This step can help minimise the risk of contaminating the patch and help remove any medicines that may accidentally stick to the skin during application.

> Rotate the site of application

Be sure to apply the patch to a new site for each application.

Rotating the site of application is crucial, as using the same site every time can potentially cause skin irritation.

Furthermore, applying the patch to the same area on a regular basis can increase the rate of medicine absorption into the bloodstream.

This, in turn, could lead to an overdose of the medicine.

This risk could also occur when applying a patch to wounded or irritated skin, as the rate of absorption is altered.

Hence, the site of application needs to be intact and non- irritated.

> Ensure the patch is intact

Patients should never use a patch that has sustained any kind of tear or damage.

This is to ensure that the release of medicine from the patch remains consistent.

A damaged patch could potentially release the active ingredient faster, resulting in unnecessary increased absorption of the medicine.

It is acceptable to get the patch wet, e.g. during a shower.

However, patients should not keep the patch under water for long periods of time, as this might cause the patch to loosen or fall off.

> Ensure the patch is applied properly

When applying the patch, press it down firmly for 30 seconds on the skin with the palm of your hand.

Once applied, check if the patch has adhered to the skin properly, especially on the edges.

The patch has to be flat against the skin with no bumps or folds in it.

> Remove the patch at the proper time

Patients should not let the patch remain attached to the skin longer than the specified duration of application.

Replace a new patch at the scheduled time as instructed by the doctor or pharmacist.

If the patch adhesive causes skin irritation, the next patch can be placed in another area.

After removing a patch, fold it in half and press firmly so that the adhesive edges stick together to seal it shut.

Throw the used patch away in a closed trash can.

Be aware that a used patch may still contain some medicine and could pose a risk to vulnerable groups at home.

> Store the patches properly

Store the patches in their protective sachets inside the original box at room temperature.

Protect the patches from direct sunlight, heat sources and high moisture.

In addition, make sure the patches are out of reach of children.

A convenient method

With ongoing advancements, transdermal patches hold immense potential as a convenient and precise method of medicine delivery.

However, it is vital to use them appropriately in order to maximise their benefits.

Conversely, they may lead to unfavourable effects if used improperly.

Hence, patients are strongly advised to consult a doctor or pharmacist if there is any confusion over the use of a transdermal patch.

For any inquiries regarding medicines, please call the National Pharmacy Call Centre (NPCC) at the toll-free number 1-800-88-6722 during weekdays from 8am to 5pm, except on public holidays.

Muhammad Adib Ahmad is a pharmacist at Hospital Keningau, Sabah. This article is courtesy of the Health Ministry’s Pharmacy Practice and Development Division. For more information, email starhealth@thestar.com.my. The information provided is for educational and communication purposes only, and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this article. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
Wellness,Know Your Medicines,drugs,transdermal patch
Transdermal patches are an effective way of delivering regular doses of medicine in a painless and non-invasive way.