Rectal drug delivery system

1. 1
Mr. Sagar Kishor Savale
[Department of Pharmaceutics]
avengersagar16@gmail.com
2015-2016
Department of Pharmacy (Pharmaceutics) | Sagar Savale
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2. CONTENT:
2
1. Introduction
2. Anatomy & physiology of rectum
3. Absorption from rectum
4. Factor influencing drug absorption
5. Monitoring drug absorption
6. Suppository
7. Enemas
8. Rectal capsule
9. Advantages
10. Disadvantages
11. Applications
12. Conclusion
13. References
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3. INTRODUCTION:
3
• History:
In the 18th century, a French pharmacist, Baume used rectal route for
administration of suppositories.
• Definition:
“Rectal drug delivery system means administration of drug or
pharmaceutical preparations via rectum for local or systemic effect.”
example: suppositories, rectum tablets and capsules, semisolids enemas, etc.
• Rectal products may be:
1. Solid unit dosage form: Suppository.
2. Liquid unit dosage form: Enema.
3. Semi-solid dosage form: Ointment, Cream.
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4. ANATOMY AND PHYSIOLOGY OF RECTUM :
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5. ANATOMY AND PHYSIOLOGY OF
RECTUM :
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 The rectum is about 15 to 20 cm
long and 1.5 to 2 cm in width.
 It hooks up with the sigmoid
colon and with the anal canal.
 It is a hollow organ with a
relatively flat wall surface,
without villi and with only three
major folds, the rectal valves.
 The rectal wall is formed by an
epithelium which one cell layer
thick.
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 The rectal tissues are
drained by the inferior,
middle and superior
haemorrhoidal veins,
but only the superior
vein connects with the
hepatic-portal system.
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7.  Under normal conditions, the rectum emptying and filling
provokes a defecation reflex which under voluntary control.
 The transverse folds in rectum keep stool in place until the
person is ready to go to the toilet.
 Rectum contains about 2 to 3 ml of mucous, which has a pH
of 7.4.
 The entire surface area of rectum is 200 - 400 cm2.
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8. ABSORPTION FROM RECTUM:
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 Medicaments absorbed in the lower part of the rectum are delivered
directly into the systemic circulation, thus avoiding any first-pass
metabolism.
 Thus keeping the drug in the lower part of the rectum would be
advisable.
 The drug in unionize with high partition coefficient is readily
absorbed.
 However, it has been found that suppositories can settle high enough
in the rectum to allow drug absorption.
 The process of absorption will be passive diffusion.
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9. Factors Influencing Drug
Absorption:
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A. Physiological factors:
1. Quantity of dissolution fluid available:
 Very small volume under normal conditions.
 Under non-physiological conditions the volume is enlarged.
 Thus, absorption of slightly soluble drugs will be dissolution rate
limited.
(e.g. phenytoin)
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2. Properties of rectal fluids
 Composition, viscosity and pH of rectal fluids have great effects
on drug bioavailability.
3. Contents of the rectum
 Faecal content
4. Motility
 Upright position
 Wave of contraction from colon
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B. Physiochemical factors:
1. Solubility:
Higher the solubility, consequently higher the
dissolution rate and better is absorption.
2. Degree of ionization:
At the alkaline pH of rectal mucosa, basic drugs will
exist in their unionized form and readily absorbed.
3. Particle size:
The smaller the size, the more readily the dissolution
of the particle and the greater the chance for rapid
absorption.
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4. pH:
Rectal content is slightly alkaline (pH 7-8) , so alkaline
drugs are quickly absorbed than acidic drugs.
5. Partition Coefficient:
Higher the partition coefficient of drug, more readily
absorption of drug.
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13. MONITERING DRUG ABSORPTION:
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 Enhancing agent:-
e.g. salicylates
bile salts
fatty acid
 pH control
 Solubilizing agents
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14. SUPPOSITORY:
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“Suppository is solid unit dosage form used for rectal
administration and which is composed of active drug molecule
with water soluble or fatty bases.”
The suppository melt at body temperature and weight
is vary in 1 g (children) to 2.5 g (adults).
 TYPE OF BASES:
BASES M.P. SOLIDIFICATION
POINT
Fatty Bases
1) Cocoa butter 30-35 24
2) Hard butter 36-45 32-40
Water Soluble Bases
1) PEG 38-49 38-42
2) Tween 61 35-49 -
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15. Methods of manufacturing of suppository:
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 Hand molding:
The base and other ingredients are triturated well then rolled
into a uniform cylinder with a large spatula and cut that cylindrical
suppository mass into required size piece.
 Compression molding:
In the compression machine, the suppository mass is placed
into a cylinder which is then closed.
Pressure is applied from one end to release the mass from the
other end into the suppository mold or die.
The additional pressure is applied to mass in the die, the formed
suppository ejected.
 Pour molding:
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16. Enemas and Microenemas
 Evacuant Enema:
Volume may be up to 2 liters.
e.g.- soft soap enemas
 Retention Enemas:
Volume does not exceed 100 mL.
e.g.- Prednisolon enemas
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17. Rectal Capsule:
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18. ADVANTAGES:
 Infants and children, who have difficulty in swallowing oral
medicine.
 Avoidance of first pass metabolism when given orally.
example- Lidocaine, Morphine.
 In cases of nausea and vomiting act as alternative route of
administration.
 Its contact with digestive fluid is avoided.
example- Penicillin, vitamins.
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 Drugs which causes gastric irritation or ulceration are administered
in rectum.
example- Aceclofenac.
 Drug absorption may be easily discontinued in an events of
accidental overdose.
 Drug absorption is not influenced by ingestion of food and the rate
of gastric empting.
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20. DISADVANTAGES:
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 Surface area of rectum is far small for absorption.
 Fluid content of rectum is much smaller.
 Microbial degradation may occur in rectum.
 Patient acceptability may be a problem.
 Development of proctitis.(inflammation of rectum)
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21. APPLICATIONS:
 Local effect:
• In case of pain, itching and hemorrhoids
• Locally active drugs include astringents, antiseptics, local
anesthetics, vasoconstrictors, anti-inflammatory drugs,
soothing and protective agents and some laxatives
 Systemic effect:
• Anti-asthmatics, anti-rheumatics and analgesics.
 Drugs administered by this route include aspirin,
paracetamol, theophylline and few barbiturates, etc.
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22. REFERENCES:
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1. Lakshmi Prasanna J., Deepthi B. and Rama Rao N., Rectal drug delivery: A
promising route for enhancing drug absorption, Asian Journal of Research
in Pharmaceutical Science, 2012, Vol-2, page no.:143-149.
2. Pushkar Baviskar, Anjali Bedse, Sayyed Sadique, Vikas Kunde and
Shivkumar Jaiswal, Drug Delivery on Rectal Absorption: suppositories,
International Journal of Pharmaceutical Science, 2013,(21)1, page no.: 70-
76.
3. D. M. Brahmankar and S. B. Jaiswal, Biopharmaceutics and
Pharmacokinetics a treatise, second edition, 2009, Vallabh prakashan,
page no.- 83.
4. Ross and Wilson , Anatomy and Physiology in Health and illness, Churchill
Livingstone, 11th edition, page no.: 277-290.
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23. 5. James Swarbrick and James C. Boylan, Encyclopedia of
Pharmaceutical Technology, second edition, volume 1, A-
D, pages 1-1032, page no.932-943.
6. www.encyclopedia.com/rectal drug delivery
(01/03/2016, 01:30pm)
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