Is expired medicine biodegradable? (5 routes of drug administration)

This blog shall answer the question of the biodegradability of expired medicine.

In addition, other areas shall also be covered. They include the following:

  • Definition of medicine.
  • Difference between drug and medicine.
  • Types of drugs.
  • Drug metabolism.
  • The future of biodegradable drugs.

Is expired medicine biodegradable?

Yes and no, expired medicine can be degraded or not depending on its active ingredients. When a drug expires, its active ingredient becomes ineffective against its target pathogen. Expired drugs can also become even more poisonous to humans or other microorganisms.

So the biodegradation of expired medicine will depend on the route the active ingredient takes; if it becomes ineffective against microorganisms, then it can easily be degraded by some microbial enzymes into some nontoxic forms.

If the medicine expires and the active ingredient becomes more poisonous and toxic, it, therefore, can not be degraded since it will harm or kill the microorganisms which should be degrading it.

In general, medicine is made to target pathogenic microorganisms. These are microorganisms that are capable of causing infections to human beings, plants, and animals.

Most pathogenic microorganisms are in the classes of viruses, bacteria, and fungi.

The pathogenicity of viruses is the highest, followed by bacteria and then bacteria.

There are very few viral drugs in the market due to virus complexity. Medicine manufactured to target bacteria is called an antibiotic, while the one made to target fungi is called a fungicide.

There is a very high number of bacterial species that cause illness, but the most common ones are plasmodium, mycobacterium, salmonella, klebsiella, rickettsia, vibrio, influenza, chlamydia, and Shigella among others.

The types of fungi include the following.

Candida, aspergillus, cryptococcus, Histoplasma, pneumocystis, and Stachybotrys. 

What is medicine?

Medicine is a chemical substance that is used to target a certain type of pathogenic microbial organism.

There are different types of medicines which range from antiviral, antibacterial, also called antibiotics and antifungal, also called fungicides.

The purpose of a medicine can be different, it can be used as a vaccine or a diagnostic medicine.

Different medicines have different active ingredients.

An active ingredient is a reactive substance that is found in medicine, it is the chemical that targets the microorganism. 

What is a drug?

A drug is any substance that can when taken, alter the normal functioning of the body.

All medicines are drugs but not all drugs are medicine. Some drugs are not taken with the sole purpose of targeting a microorganism, some are taken for pleasure.

There are different categories of drugs which include the following.

Prescription drugs.

These are types of drugs that are used to target a pathogenic microorganism.

They are also called medicine.

They can be antiviral, antifungal, or antibiotic. They can also be painkillers or anesthetics.


These are types of drugs that give the user “a high” feeling.

They are used to stimulate the nervous system and interfere with body coordination.

They can be classified as hard stimulants or mild stimulants.

Hard stimulants are those hard drugs that contain very strong active ingredients. These examples include cannabis Sativa (bhang, or marijuana) which contains cannabinoids, morphine, heroin, khat, and many others.

Mild stimulants contain chemicals that are not very strong and therefore do not have a very big impact on the body.

They include drugs like tobacco cigarettes, tea, and coffee which contain caffeine and nicotine respectively, and gum for some users.


These are drugs that are derived from poppy plants. They are used as painkillers and are also used for pleasure as stimulants.


These are drugs that are used for depressing the nervous system.

They interfere with the normal functioning of the nervous system, therefore affecting brain activities like balance, good judgment, memory, and posture.

A good example in this category is an alcoholic beverage.


These are a class of drugs that relieve the body of any pain.

They include anti-inflammatory analgesics which relieve inflammation pain and opioid painkillers which alters the brain from perceiving pain.

How is medicine administered in the body?

There are several ways in which drugs and medicine can be administered in the body.

These methods of drug administration are also called routes of drug administration.

They include the following.

Oral route of administration.

This is a form of administration where medicine is taken to the body through the mouth.

This is a very common method for solid drugs like pills, tablets, or capsules.

Anal and vaginal route.

The solid drug can be administered through the anal or vaginal routes depending on the target pathogen or the condition of the patient.

Anal drug administration is most administered to unconscious or patients with poor coordination.

Intravenous drug administration.

This is a type of drug administration where the drug is directly injected into the blood veins.

This method is very effective for emergency medication or for drugs that should bypass first-pass metabolism (degradation of drugs in the liver) for them to be effective.

The drug is taken directly to the blood and therefore to the brain. The effects are felt almost immediately.

Subcutaneous drug administration.

The subcutaneous layer is a fat layer between the skin and the muscles.

The drug is administered in this fatty layer using a small needle. The drug must therefore be fat-soluble.

Drug absorption into the blood system is very low and can take even 24 hours. This method is good for drugs that need a long time of activity.

The transdermal route of administration.

This is a drug administration method whereby the drug is passed through the skin and into the blood system.

The drug is mostly administered as a patch or ointment and slowly diffuses into the blood and to the brain.

Sublingual route of drug administration.

This route entails drugs being administered through the lower part of the mouth, under the tongue.

The drug, mostly in the form of a pill or tablet, is slowly absorbed by the cells of the buccal cavity and taken to the brain.

Inhalation route of drug administration.

This is a form of administration whereby the drug is inhaled as fumes through the nasal or the buccal cavity.

Drugs are mostly in the form of droplets and upon inhalation, they vaporize into fumes and are absorbed into the body system.

How is the drug biodegraded in the body?

Upon reaching the body, drugs are broken down into forms that are non-toxic to the body.

This method of drug degradation by enzymes is called drug metabolism or more scientifically, drug biotransformation.

This process occurs in almost everybody’s organs but the main organs are the liver, skin, kidney, lungs, and the gastrointestinal tract.

Drug biotransformation occurs in 2 main steps:

Phase I biotransformation.

This is the first phase of drug metabolism. It involves changing the state of the drug into an active substance by activating the active ingredient of the drug.

The reactions that occur in this phase are; reduction, oxidation, hydrolysis, cyclization, and decyclization.

The process involves cytochrome P450 enzymes such as monooxygenase and oxidase enzymes and adding oxygen or removing hydrogen atoms from the drug 

The process makes the drug more polar and therefore transforms the drug from lipophilic to hydrophilic.

Phase II biotransformation.

This phase involves making the polar drug from stage I non-polar.

It is the detoxification stage whereby the drug’s active ingredient is deactivated.

It involves processes like conjugation of the active ingredient with another molecule like glutathione, sulfate, and glycine.

It involves conjugation enzymes like glutathione s-transferase.

The stage involves reactions such as methylation, sulfation, and acetylation. The drug loses its permeability to the cell membranes and can only be transported by biological carriers such as proteins.

At this stage, the drug is ready for excretion from the body.

Is expired medicine eco-friendly?

No, expired drugs are not eco-friendly and should not be disposed of in the environment.

According to a study report, some drugs may be effective against microorganisms even long after their expiry and as a result, they still affect microorganisms and are therefore not degraded.

This results in their accumulation in the soil and water bodies, and are ingested by fish.

The drugs may affect the fish or other aquatic life or they may also affect people who ingest fish that have ingested these drugs. 


This article has covered the question of expired medicine biodegradability.

In addition, other areas have been covered which include:

  • Categories of drugs.
  • Types of drug administration.
  • Drug metabolism and biotransformation.
  • Eco-friendliness of expired medicine.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is expired medicine biodegradable?

What is non-biodegradable?

Non-biodegradation is the inability to decompose or be broken down by microorganisms.

Can you flush pills down the toilet?

Yes, the Food and Drug Administration (FDA) advises that some medicines can be dumped in the toilet to prevent the accumulation of toxic drugs in the environment.

How long can you take medicine after the expiration date?

It is advisable not to use the medicine after its expiry. This is because some expired drugs might be poisonous or the efficacy of the medicine has been lost and therefore not effective to do its intended purpose.


S. W. Johnny Lau, Darell R. Abernethy(2022). Drug Biotransformation: Medical therapy in older adults.

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Guengerich FP (June 2001). “Common and uncommon cytochrome P450 reactions related to metabolism and chemical toxicity”. 

Chem. Res. Toxicol. 14 (6): 611–50. 


Jakoby WB, Ziegler DM (December 1990). “The enzymes of detoxication”. J. Biol. Chem. 265 (34): 20715–8. doi:10.1016/S0021-9258(17)45272

Mylonaki I, Allémann É, Saucy F, Haefliger J-A, Delie F, Jordan O (2017). “Perivascular medical devices and drug delivery systems: Making the right choices”. Biomaterials. 128: 56–68. 

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