Injections, suppositories and other dosage forms

Photo of a man inhaling medicine
PantherMedia / Alexander Raths

Medications are supposed to reach the part of the body they are intended to affect. So manufacturers choose a suitable dosage form when they produce the medication. The dosage form is the physical form that medication is used in. Tablets and ointments are just two of the many different possible dosage forms.

The most suitable dosage form depends on various things, including what physical and chemical properties the medication has and where it should take effect. For example, medicine that is meant to have an effect on the lungs can be breathed in (inhaled). Medication for treating a vaginal can be inserted using a vaginal suppository. Medicines that are absorbed into the body through the mucous membranes lining the mouth can also be taken in the form of chewing gum. One well-known example is nicotine gum for helping to quit smoking.

Injections

In injections, the active ingredients (those responsible for the medication's effect) are dissolved in a liquid. Medication is often injected into a vein (intravenous administration) if it needs to work as fast as possible, for instance in an emergency. If the medication should have a slower effect or if it shouldn't enter the bloodstream directly, it can also be injected into a muscle (intramuscular) or into fat tissue beneath the skin (subcutaneous).

Some medications have to be injected because they would break down in the stomach or bowel otherwise. Insulin is one example. Most vaccines also have to be injected for this reason. Many injection solutions only keep for a short time after they are opened if they're not cooled.

Hygiene is especially important when dealing with injection solutions, syringes and needles. They need to be kept free of germs (sterile) because germs could easily enter the body otherwise. They need to be disposed of safely after use to avoid injury.

Infusions

Also known as drips, infusions usually involve having a tube placed into a vein (venous ) for some amount of time. The liquid then enters the bloodstream through this tube. Infusions are used when there's no other or better way to steadily deliver a drug or a liquid to the body for a certain period of time.

A venous may also be important if medications need to be injected into the bloodstream very quickly in an emergency. For this reason a venous is inserted in many operations, just in case. To prevent germs from getting into the bloodstream, hygiene is very important when administering infusions as well.

When people are given infusions repeatedly over a longer period of time, a port system can also be used. These systems consist of a flat container with a thin tube. The port system is implanted under the skin during a minor operation, for example near the collar bone. The small container can be refilled by injecting the medication through the skin and into the container using a syringe. The container slowly releases the medication, which travels along the tube into the vein. Port systems can remain under the skin for several weeks, where they are protected from . They're used in chemotherapy for cancer, for example.

To relieve pain in or numb part of the body, anesthetics can be injected through a into the epidural space (the area between the protective layers of the spinal cord and the spinal column). The anesthetic numbs the nerves, preventing touch and pain signals from being sent to the brain.

Illustration: Delivering pain-numbing drugs near to the spine: Epidural and spinal anesthesia

Delivering pain-numbing drugs near to the spine: Epidural and spinal anesthesia

Here a is inserted into the epidural space and anesthetics can then be given repeatedly through the as needed, without having to use a syringe every time. Pain-relieving infusions can also be given like this, for example to reduce labor pain during childbirth (an "epidural").

Spinal anesthesia (also known as a spinal block) works a little differently: The medication is injected closer to the spinal cord – into the liquid-filled area that surrounds the spinal cord (the subarachnoid space). This causes the lower half of your body to feel numb.

Slow-release: Implants and injections

Slow-release implants are made of foreign material that is put into the body, and remains there for a longer time to continuously release medication. When the effect weakens, the implant is removed or it dissolves on its own. This approach allows the drug to have a steady effect over several months. One example is a hormonal contraceptive implant.

Injections of slow-release medication are injected under the skin or into muscle tissue, and the ingredient that is responsible for the effect is only gradually released. This can be achieved by mixing this active ingredient with oils or special salts that the body can only break down slowly. Examples of slow-release injections include long-acting insulin, extended-release steroid injections and the three-monthly birth control shot.

Suppositories

Some medications can be inserted into the anus (bottom) as a rectal suppository. They may contain drugs that are specifically meant to have a local effect in the bottom. But suppositories can also be used to treat other parts of the body. Then the active ingredients are absorbed through the lining of the bowel and travel through the bloodstream to the part of the body where they are supposed to have an effect. Suppositories are often used when it's difficult to take medication orally, for example if people are likely to vomit or when children have a fever and don't want to, or can't, take a tablet.

Vaginal suppositories are inserted into the vagina to treat things like inflammations or fungal infections there. The suppositories dissolve in the vagina and release their active ingredients. Some tablets and creams can also be inserted into the vagina. They usually come with a plastic insertion aid (applicator).

Drops, ointments and sprays for the eyes, ears and nose

Some medications come in the form of drops. These can be applied, for example, directly to the eye or ear to treat things like eye or ear infections. Ear drops should not be too cold when applied because they might cause pain or dizziness otherwise. There are also eye ointments and gels that are applied to the inner side of the lower eyelid. It is especially important to keep eye medications germ-free.

Nasal drops and sprays can be used in the short-term treatment of colds and allergies. Either a certain number of drops are put into the nose using a pipette, or a specific amount of the medication is sprayed into the nose. It’s important to keep the pipette (dropper) squeezed when removing it from the nose, so that the medication is not contaminated by nasal discharge.

Inhaled medication

Medications that are breathed in (inhaled) can be a good idea if they are meant to have an effect directly in the lungs. Many asthma medications are available as sprays that are inhaled, for example. Because the lungs have such a good blood supply, though, medications that are meant to have an effect throughout the body can also be breathed in. One well-known example is general anesthesia, where the anesthetic is breathed in through a mask.

When a liquid or solid active ingredient is finely suspended in air or gas, the mixture is called an aerosol. Aerosols can be applied using medical devices such as metered dose inhalers. These finely disperse the drug and combine it with a propellant gas. This is how you use it: breathe out, close your lips around the mouthpiece, press the spray activation (puff) and then at the same time breathe in deeply. The finer the liquid or powder is dispersed, the deeper it can enter the lungs. It is important to give the device a regular, thorough cleaning, since it always touches the inside of your mouth when you inhale while using the device, and could come into contact with germs.

Substances like essential oils can also be breathed in using hot steam, for example to relieve cold symptoms. Hot water allows the oils to vaporize more quickly, increasing their effect on the mucous membranes.

Friedland J. Arzneiformenlehre für PTA. Stuttgart: WVG; 2013.

Kretz FJ, Reichenberger S. Medikamentöse Therapie. Arzneimittellehre für Gesundheitsberufe. Stuttgart: Thieme; 2007.

Lüllmann H, Mohr K, Hein L. Taschenatlas Pharmakologie. Stuttgart: Thieme; 2014.

Plötz H. Kleine Arzneimittellehre für Fachberufe im Gesundheitswesen. Heidelberg: Springer; 2017.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on August 24, 2021
Next planned update: 2024

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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