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Taking Medication Designed for Oral Use Sublingually or Rectally -A Cautionary Approach

The administration of medication, especially when it comes to oral tablets, is a well-established practice in healthcare. However, there has been increasing interest in alternative routes of administration, such as sublingual (under the tongue) or rectal administration, for medications originally designed for oral use. While it may be tempting to explore these unconventional methods, it’s important to approach them with caution. The reason for this caution is simple: there is a lack of comprehensive research and data regarding the safety, benefits, or potential risks of taking oral tablets in this manner.

Gender-Affirming Medications

Some people consider taking medicines such as estrogen or progesterone tablets or capsules in a different way than recommended by the manufacturer. However, it is always best to take them as instructed by the leaflet in the packaging.

  • Estrogen tablets should be taken orally
  • Progesterone (eg utrogestan) capsules should be taken orally
  • Progesterone pessaries (eg cyclogest) can be inserted into the vagina or the rectum

People who have had a new vagina created through gender-affirming surgery should consider which type of tissue their vagina is made of. If it is constructed from colon then it follows that pessaries and suppositories would be absorbed from there. If it is made from penile inversion then absorption may be markedly reduced, and rectal insertion would be better.

Understanding Pharmacology

To grasp the significance of this caution, it’s essential to understand the concept of pharmacology. Pharmacology refers to the study of how drugs interact with the body, including their mechanisms of action, absorption, distribution, metabolism, and elimination. Each medication is carefully formulated to ensure its effectiveness and safety when taken as directed.

The Unknown Impact

When a medication is designed for oral use, it undergoes specific formulation and testing processes to optimise its pharmacokinetics (how the body processes the drug). These processes consider factors such as safety (eg would the coating of a tablet cause damage to the rectum), bioavailability (how much of the drug enters the bloodstream), timing of release, and potential interactions with other substances.

Taking medication sublingually or rectally alters the drug’s route of administration and may affect its pharmacokinetics. However, the key concern is that the research and clinical trials that support the safety and effectiveness of a medication are typically conducted with the recommended oral administration method in mind.

Lack of Data

The primary issue with sublingual or rectal administration of oral tablets is the lack of data to inform healthcare providers and patients about the potential consequences. We don’t have comprehensive studies to determine how the pharmacology of these medications will be affected when taken through alternative routes. We don’t know how effective it will be and how safe it will be.

A Prudent Approach

Given the uncertainties surrounding sublingual and rectal administration, the general recommendation remains to take medication that is designed to be swallowed as a tablet precisely as directed—swallowed as a tablet. This approach aligns with established medical practices and ensures that the medication’s effectiveness and safety are upheld.

Exceptions to this guideline may occur when individuals have difficulty swallowing or when oral administration is not possible due to specific medical conditions. In such cases, people may explore alternative forms of medication, such as gels, sprays, liquids, injections, or medications specifically designed for sublingual or rectal use.


Monitoring hormone levels is a critical aspect of hormone replacement therapy (HRT) to ensure safety and efficacy. However, if an individual chooses to take their tablet in a different way than prescribed, monitoring must be based on the available information related to that specific medication and administration method. Deviating from the prescribed route of administration may impact how the medication is absorbed and metabolised in the body, potentially affecting hormone levels. However, we can only apply monitoring protocols based on the known characteristics of the medication and this may affect safety and effectiveness.


While the idea of sublingual or rectal administration of oral tablets may appear innovative, it’s essential to prioritise safety and effectiveness. Until more research and data become available, following the recommended method of administration remains the best practice to ensure that medications provide the intended therapeutic benefits while minimising potential risks. Always consult with a specialist for guidance on the appropriate route of administration for your specific medication and condition.

Updated on January 31, 2024

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