Rectal Drug Delivery

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  • Created by: LBCW0502
  • Created on: 23-11-19 12:11
When is rectal drug delivery used?
When the patient is not able to make use of the oral route (problem with GIT, nausea, post-operative). Age of patients (babies, older patients). API is less suited for oral administration. Unwanted effects, unpleasant taste
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Why is rectal drug delivery used? (1)
Treatment of local pathologies, chronotherapy (asthma, HTN, cardiac arrhythmias, arthritis, inflammation). Greater responsiveness to absorption enhancers. Less enzymatic activity. Site for delivery of delicate drugs (peptides, proteins)
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Why is rectal drug delivery used? (2)
Oral delivery of vaccines as it is rich in lymphoid tissue
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What are the advantages of rectal delivery?
Offers alternative to PO, useful when patient cannot swallow the drug (unconsciousness, vomiting patients, serious GIT disturbances, children) or when we need to avoid local adverse reactions (e.g. NSAIDs)
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What are the disadvantages of rectal delivery?
Poor compliance, some API can cause local irritation of rectal mucosa, stability of dosage form during high temperature, melted suppository matter may come out
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What are the common API classes used in rectal delivery?
Opioids analgesics, NSAIDs (diclofenac), anti-pyretics (paracetamol), anti-emetics (thiethylperazine)
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How does the API enter into the system via rectal delivery? (1)
API enters systemic circulation (middle and lower hemorrhoidal veins, iliac vein, inferior vena cava - by pass liver, no first pass effect). API can pass through portal circulation via upper hemorrhoidal veins, inferior mesenteric vein
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How does the API enter into the system via rectal delivery? (2)
Hepatic portal liver - first pass effect can take place
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Describe features of the colon/rectum anatomy
Rectum forms 150-220 mm of the GIT. Flat surface, no villi, three major folds, rectal wall formed by epithelium (cylindrical cells and goblet cells), pH of 7.5
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Describe features of the rectum anatomy
Venous drainage of human rectum. Lower and middle hemorrhoidal drain in systemic circulation. Upper and hemorrhoidal drains to portal vein
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Describe the drug release from a suppository (1)
Solid at room temperature, melts at body temperature, spreading of particles, deposition of particles on surface of rectum (presence of mucus/watery layer)
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Describe the drug release from a suppository (2)
Particles get wet (dry particles have layer of fat/wax, dispersed by surfactants) in presence of factors e.g. sodium carbonate, dissolution, drug absorption
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Describe the drug release from a suppository (3)
Properties of rectal mucus important for wetting of particles. Surfactants aid wetting process (introduce water into drug particles)
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Which factors affect absorption from the rectum?
Quantity of fluid available for the drug dissolution (3 mL). Properties of rectal mucus. Contents of rectum. Motility of rectal wall
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Describe features of suppositories (1)
Different shape and size, drug content (0.1-4.0%), usually up to 4 g (more drug can be used in the rectal route compared to using the oral route
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Describe features of suppositories (2)
Vehicle (suppository base). Semi-synthetic : glyceride type fatty bases, water soluble bases (gelatin). Requirements - melting range (rapid solidification to prevent segregation), viscosity of molten base, chemical and physical stability for storage
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Describe features of suppositories (3)
Semi-synthetic (glyceride type fatty bases, hard fat is a mixture of mono, di, triglyceride esters of higher saturated fatty acids). Melting range 33-40 degrees Celsius, iodine value <3 (relates of oleic acid content)
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Describe features of suppositories (4)
OH value <50 (indicates amount of mono and diglycerides). Water soluble - glycerol, gelatin or soap bases (laxative purposes or vaginal therapy), macrogols: PEGs
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Describe features of suppositories (5)
Drug solubility and dispersibility in vehicle will direct type of product (solution of suspension), choice of vehicle will depend on partition co-efficient vehicle/water and rate of release. Drug surface properties. Drug particle size. Amount of drug
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Which additives are used in suppositories?
Colloidal silica oxide or aluminium monostearate (1-2%) to increase viscosity (high viscosity more favourable), surfactants, wetting agents or preventing agglomeration
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Outline suppository manufacturing (1)
Melting the vehicle, mixing the drug and the molten vehicle. Dispensing in a former cooling to solidify. Packing in the container (PVC or aluminium foil).
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Outline suppository manufacturing (2)
Mix suppository base with drug particles, mix at particular temperature, pour into mould, needs to solidify immediately, if it doesn’t become solid quickly (sediments, problematic dose, uneven distribution of dose in suppository, separate powder/base
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Which factors are check during suppository QC?
Appearance, weight, disintegration, melting/dissolution, mechanical strength, content of active ingredient, release
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Which factors are considered during suppository QC (drug release from suppositories, tests in vitro)?
Temperature, contact area, release medium, movements, membranes
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Give examples of other rectal formulations
Fatty ointments (for haemorrhoids). Large volume (100 mL) enemas (rectocolitis), tablets that release CO2 for systemic administration, soft shell capsules, microenemas (3 mL)
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Other cards in this set

Card 2

Front

Why is rectal drug delivery used? (1)

Back

Treatment of local pathologies, chronotherapy (asthma, HTN, cardiac arrhythmias, arthritis, inflammation). Greater responsiveness to absorption enhancers. Less enzymatic activity. Site for delivery of delicate drugs (peptides, proteins)

Card 3

Front

Why is rectal drug delivery used? (2)

Back

Preview of the front of card 3

Card 4

Front

What are the advantages of rectal delivery?

Back

Preview of the front of card 4

Card 5

Front

What are the disadvantages of rectal delivery?

Back

Preview of the front of card 5
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