A suppository is a solid dosage form of medication that is inserted into a body cavity, typically the rectum or vagina, where it dissolves or melts to release the drug. This method of drug delivery is often used as an alternative when oral administration is not possible, such as when a person is experiencing nausea, vomiting, or is unable to swallow tablets. Once inserted, the medication is released to act directly on local tissues or be absorbed into the bloodstream for a systemic effect.
The body cavity used for insertion, most commonly the rectum, is highly vascularized, meaning it contains many small blood vessels that can absorb the medication. When a suppository is placed in the lower rectum, it allows a significant portion of the drug to bypass the liver’s first-pass metabolism, which can increase the amount of medication that reaches the general circulation. This mechanism makes suppositories a useful option for delivering both localized treatments and drugs intended to affect the entire body.
Typical Onset Times for Different Suppository Types
The time it takes for a suppository to work depends heavily on whether it is designed for local action or systemic absorption. Suppositories intended for local effects, such as laxatives, tend to have the fastest onset time. A glycerin or bisacodyl laxative suppository works by irritating the rectal lining or drawing water into the area to stimulate a bowel movement.
These local-action suppositories often produce an effect rapidly, typically within 15 to 60 minutes after insertion. For instance, glycerin suppositories can trigger a result within 5 to 15 minutes, while bisacodyl suppositories usually work within 15 to 60 minutes. This quick response is due to the medication directly stimulating the local tissue rather than needing to fully enter the systemic circulation.
In contrast, suppositories designed for systemic absorption, such as those containing pain relievers or anti-nausea medication, require the active drug to dissolve and cross the rectal lining into the bloodstream. For these medications, the onset of action is generally longer, often taking 30 minutes to one hour before the user begins to feel the therapeutic effects. The time to reach the peak concentration in the blood, which corresponds to the maximum effect, can extend to two hours. The precise timing is influenced by the drug’s formulation and how quickly the suppository base releases the medication.
Key Factors That Influence Absorption Speed
The speed at which a suppository delivers its medication is significantly influenced by the suppository’s physical composition, particularly the base material. Suppositories are generally made from either fatty bases, like cocoa butter, or water-soluble bases, such as polyethylene glycol or glycerinated gelatin. Fatty bases melt quickly at body temperature, which allows for a rapid release of the drug.
Water-soluble bases, however, must dissolve in the small amount of rectal fluid present before the drug can be released and absorbed. If the patient is dehydrated, this dissolution process can be slowed, which delays the onset of action. The drug’s formulation itself also matters, as a drug’s solubility and particle size directly affect how easily it dissolves in the rectal fluid and passes through the mucosal barrier.
Physiological factors in the body influence absorption speed, most notably the local blood circulation. The rectum has a rich network of blood vessels, and the efficiency of blood flow in this area determines how quickly the absorbed drug is carried away and distributed throughout the body. Additionally, the presence of fecal matter in the rectum can act as a barrier, physically preventing the suppository from making proper contact with the mucosal wall, which severely hinders the absorption rate.
Ensuring Proper Administration for Maximum Effectiveness
To ensure a suppository works within its expected timeframe, proper technique during administration is necessary. Before insertion, the user should attempt to empty their bowels, unless the suppository is a laxative, to ensure the medication has direct contact with the rectal wall. The suppository should be unwrapped and, if needed, dipped briefly in water or lubricated with a water-based product to ease insertion. Petroleum jelly or oil-based lubricants should be avoided because they can interfere with the suppository’s dissolution and the drug’s absorption.
The suppository must be inserted beyond the internal anal sphincter, typically about one inch for an adult, to prevent it from being expelled. Insertion past this muscular ring allows the suppository to rest against the rectal mucosa where absorption is maximized. After placement, remaining still, often by lying down for 15 to 30 minutes, is important to allow the suppository base to fully melt or dissolve. This retention time ensures the medication is not expelled prematurely.
What to Do If a Suppository Does Not Work
If the expected time frame for the suppository to work has passed without any noticeable effect, the first step is to avoid immediate re-dosing. Inserting a second suppository without professional advice can lead to an overdose or an exaggerated effect when the first dose finally begins to act. A common reason for failure is the suppository being expelled or not inserted deeply enough past the anal sphincter.
If a laxative suppository has not worked within the maximum specified time, usually 60 minutes, or if symptoms are worsening, contact a healthcare provider. For non-laxative suppositories, if the condition being treated, such as severe nausea or pain, does not improve, medical guidance is necessary. A doctor or pharmacist can help determine if the failure is due to improper placement, poor absorption, or a need for an alternative treatment.