DRUG ADMINISTRATION BY THE RECTAL ROUTE
The rectum is the cavity of the body through which the drug is to be administered. From there the drug is readily be absorbed well. Drug administered by this route is useful when the medication can not be administered orally in case of nausea, vomiting.
The drug usually administered by the rectal route in the dosage form is semi-solid suppository. The absorption of suppositories from the rectum is influenced by the such factors like the base used in suppository, the usage of surfactant, several additives etc. Sometimes liquid or solid dosage form also is to be inserted as doctor advices.
The drug is administered into the rectum cavity from where the drug is released to give the local effect or it is absorbed to provide the systemic effect.
The rectum is linked with three vein i.e. middle rectal vein, lower inferior rectal vein and upper rectal vein. Those first two vein i.e. middle and lower rectal vein help to drain the medications directly into the systemic blood circulation and the upper vein helps to drain the drug into the portal system from where it again goes to the liver. So, you can see some portion of drug absorbed from the rectum is subjected to the first pass metabolism in the liver. The dissolution of drug is mostly affected by the fluid which is created in rectum.
The advantages of rectal route of drug administration are:
- It is suitable for the patients with nausea, vomiting and also for the unconscious patients. Because the drug is unable to be administered orally. It is also useful in case of uncooperative patients like children, mentally disturbed patient, dysphagia.
- It is most preferable route of drug administration when the drug causes the irritation in gastrointestinal tract.
The disadvantage of the route is drug absorption from the rectal cavity is sometimes irregular and unpredictable in comparing with another route of drug administration and may produce the tendency of several effect.
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