How is Chemotherapy Administered?

Chemotherapy drugs can be administered in several ways.

The method of administering any chemotherapy agent and its dosage is determined through rigorous testing (clinical trials) carried out before the drug is made commercially available for use with patients.

During the clinical trials, doctors and scientists establish how specific chemotherapy drugs are absorbed and how they work in the body. Since stomach juices are known to destroy certain chemicals, it sometimes becomes impossible to give the drug as a pill. Other types of drugs work more effectively in fighting cancer when they are administered intravenously (through a needle in the vein). Certain medications can be administered via an injection into the muscle while others are absorbed in the body when administered directly into the abdominal cavity or the bladder.

Oral chemotherapy medications (taken via the mouth)

Oral chemotherapy medications are drugs that can be swallowed. Available in forms such as tablets, pills, capsules and liquid, these get absorbed in the stomach or under the tongue.

  • Oral chemotherapy medications that are taken via the mouth have a protective coating that is dissolved by the digestive juices present in the stomach.
  • When stomach acids break down the protective coating, the medication is released and absorbed via the lining of the stomach.
  • Certain medications have a special type of protective coating that allows the medication to be released at different time intervals inside the system. Known as an extended release, this process allows a longer time delay between two consecutive doses.
  • Chemotherapy agents that can be taken by placing them under the tongue are known as sub-lingual chemotherapy medications. These dissolve and are absorbed quickly into the body. This is a quick way of administering drugs to the body. Certain medications such as anti-nausea drugs are especially effective when taken this way since they will not be lost in case the patient vomits.
  • Why aren’t all chemotherapy medications available in oral form? Some drugs can be denatured by stomach acids; others may not bet absorbed via the lining of the stomach or intestines. When they are not absorbed by the body, they are passed via the stool or urine, which renders them ineffective. Other chemotherapy drugs can be too harsh and can damage the stomach’s lining.
  • A few chemotherapy medications can be administered both intravenously and orally. Medical providers decide based on the potency of the drug, convenience and the prescribed regimen.

Chemotherapy treatment: Subcutaneous injection

  • Subcutaneous injections (sub-q) make use of a small needle, similar to those that diabetics use for taking insulin.
  • When medication is administered subcutaneously, the needle enters the space between the skin and muscle. It does not enter the muscle layer.
  • Subcutaneous chemotherapy injections are generally used for administering some specific types of chemotherapy drugs and biological response modifiers.
  • If the patient’s blood counts are below normal, subcutaneous injections are less likely to result in bleeding in comparison to intra-muscular injections.

Intra-muscular chemotherapy injections

  • Intra-muscular injections are administered via the skin to reach the muscle layer. Compared to subcutaneous injection, a larger needle is used, allowing deeper penetration.
  • Medication is absorbed more rapidly than in oral ingestion, but it slower than in intravenous, subcutaneous and sub-lingual modes of administration.
  • Intra-muscular injection is commonly used for administering anti-nausea medications since it can bypass an already upset stomach.
  • The majority of chemotherapy medications cannot be administered via the intra-muscular mode due to the harshness of chemicals.
  • Doctors often avoid intra-muscular injection when treating patients with low platelets because bleeding inside the muscle can lead to complications.


Related: Duration of chemotherapy

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