Injections, suppositories and other dosage forms

Photo of man inhaling (PantherMedia / Alexander Raths)

For medications to reach the right place inside the body, a suitable dosage form is selected when they are produced. Tablets and ointments are just two of the many different possible dosage forms.

The dosage form depends on various things, including what physical and chemical properties the medication has and where it should take effect. Medicine that should have an effect on the lungs can be breathed in, for example. Medication for treating a vaginal infection 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.


In injections, active ingredients are dissolved in a liquid and then injected. Medication is often injected into a vein (intravenous administration) if it is to have as fast an effect as possible, for instance in an emergency. This avoids a longer uptake time through the gastrointestinal tract. If the medication is to 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: otherwise, they would break down in the stomach or bowel. 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 enter the body very easily otherwise. After use the instruments must be disposed of safely.


Infusions (also called drips) usually involve having a tube placed into a vein (venous catheter) for some amount of time. Liquid then enters the bloodstream through this tube. Infusions are used when there's no other or better way to steadily administer a drug or a liquid to the body for a certain period of time.

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

When people are given infusions repeatedly over a longer period of time, port catheter systems can also be used. They consist of a flat container with a thin tube that is implanted under the skin during a minor operation, for example near the collar bone. This 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 catheter systems can remain under the skin for several weeks, where they are protected from infection. They're used in chemotherapy for cancer, for example.

To relieve pain or numb part of the body, anesthetics can be injected through a catheter into the epidural space. The drug numbs the nerves, stopping the transmission of touch and pain signals to the brain.

A catheter is inserted into the epidural space through which then anesthetics can be administered repeatedly and 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 (PDA).

Spinal anesthesia (partial anesthesia) works a little different:  Here, the medication is injected directly into the subarachnoid space containing the spinal fluid, causing the lower half of the body to feel numb.

Depot (slow-release) implants and injections

Depot 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. This approach enables the drug to have a steady effect over several months. One example is a hormonal contraceptive implant.

In depot injection, a medication is injected under the skin or into muscle tissue, and the active ingredient is only gradually released. This can be achieved by mixing the active ingredient with oils or special salts that the body can only break down slowly. Examples of depot injections are longer-acting insulin, cortisone depot injections and the three-month injection for contraception.


Some medications can be inserted into the anus (rectal) as a suppository. They may contain active ingredients that are to have a local effect. But it is also possible to use rectal suppositories containing medication that is meant to have an effect elsewhere in the body. The active ingredients are absorbed by the lining of the bowel, enter the bloodstream and then have an effect in another place. Suppositories are often used when it is difficult to take drugs orally, for example if people are likely to vomit or when children have a fever and do not want to, or cannot, 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 ointments can also be administered vaginally. They usually come with a plastic insertion aid (applicator).

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

There are medications in drop form for treating eye and ear infections, for example, that are applied directly to the eye or ear. Ear drops should not be allowed to get too cold, otherwise they can cause pain or dizziness. 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.


Medications that are breathed in (inhaled) can be a good idea if they are 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 an active ingredient that is liquid or solid is finely suspended in air or another 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 the mouth when you inhale while using the device. This can attract germs.

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