Solid Oral Dosage Forms - Tablets Flashcards
(60 cards)
1
Q
Advantages of tablets
A
- Convenient to handle
- Oral route is convenient and safe route
- Chemical and physically more stable compared to liquid dosage forms
- Preparation procedures enables accurate drug dosage
- Easily and consistently mass-produced at low price
2
Q
Disadvantages of tablets
A
- Cause local irritation effects
- Cause harm to the GI mucosa
- Drugs with low water-solubility or absorption affect the bioavailability
3
Q
2 parts in tablet manufacturing
A
- Compression: reduction in volume of a powder owing to the application of a force
- Compaction: formation of a porous specimen of defined geometry by powder compression
4
Q
Compaction cycle
A
- Die filling - gravitational/centrifugal filling of powder from a hopper into the die
- Tablet formation - upper & lower punch presses the powder in the die to form the tablet and then decompress
- Tablet ejection - lower punch rises to the top of the die, pushing the tablet upward -> removed by removing device
5
Q
Types of tablet presses
A
- Single punch press (eccentric press) -> make 1 tablet every time
- one die and one pair of punches
- lower punch is stationary while pressure is applied by the upper punch
- tablet size is controlled by the lower punch (volume fill)
- output: 200 tablets/min - Rotary press
- Have a no. of dies and punches mounted in a circle in the die table
- 1 die for 1 pair of punches always -> consistency
- 10,000 tablets/min
- both punches operate together during compression - Computerized hydraulic press
Used for evaluation of tabletting properties of powders and for predication of scale up on the properties of the formed tablets
6
Q
What powder characteristics must be controlled for a successful tabletting operation?
A
- Flowability
- Homogeneity & segregation tendency
- Compression properties and compactability
- Friction and adhesion properties
7
Q
Ways of tablet production
A
- Granulation - wet granulation: mixing -> agglomeration -> drying -> milling -> mixing -> tabletting
- Direct compaction (dry mixture): mixing -> tabletting
8
Q
Advantages of tablet production via direct compaction
A
- Powder mixing then tabletting - reduce time and cost
- no heat/water is involved -> more stable
9
Q
Disadvantages of tablet production via direct compaction
A
- large particles must be used which may be difficult to mix to high homogeneity -> segregate
- Even coloring of tablets may be difficult to achieve
10
Q
Functions of tablet excipients
A
- Filler
- Binder
- Antiadherent
- Lubricant
- Glidant
- Flavour
- Sorbent
- Colorant
- Disintegrant
11
Q
Filler
A
Added so that formulation has a sufficient bulk to be compressed into a tablet
12
Q
Examples of filler
A
Lactose, microcrystalline cellulose, dicalcium phosphate, sugar, starch
13
Q
Preference of a diluent for a poorly soluble drug
A
sucrose>lactose>dicalcium phosphate>starch
14
Q
Disintegrant
A
- Facilitate water uptake
- Rupture the tablet
- Rupture the tablet by gas production
Used to ensure that granules/tablets will break up into small fragments for rapid dissolution of the contained drug.
Insufficient -> decrease in disintegration/dissolution -> incomplete absorption of a drug
15
Q
Binders
A
Used to ensure that granules/tablets have the required mech strength. Excessive would affect the disintegration. Usual amounts: 2-10% of tablet weight
16
Q
Examples of binders
A
HPMC, PVP, microcrystalline cellulose, pregelatinized starch, gelatin, acacia
Preference: PVP>acacia>HPMC>gelatin
17
Q
Glidant
A
Used to improve the flowability of powder/granules into the tablet die during tabletting to ensure weight uniformity of tablets produced
Improve flow by adhering to the particle surface of other ingredients and reduce interparticulate friction
Many are hydrophobic
18
Q
Examples of glidant
A
talc and colloidal silicon dioxide
19
Q
Lubricant
A
Used to reduce friction between the tablet and the die wall so that it is ejected without physical defects
Many are hydrophobic
20
Q
Antiadherent
A
Used to reduced adhesion between the powder and the punch faces to prevent sticking to the punches
21
Q
Examples of antiadherent
A
Magnesium stearate, talc, starch
22
Q
Sorbent
A
Used to absorb some quantities in an apparently dry state to ensure dryness
23
Q
Examples of sorbent
A
Microcrystalline cellulose and silica
24
Q
Flavor
A
Used to give the tablet pleasant taste or to mask unpleasant taste
Normally thermolabile and should not be added prior to an operation involving heat
Often mixed with the granules as an alcohol solution
25
Function of Colorant
Used to aid identification and patient compliance
| Often achieved during coating/compaction
26
Classify Tablets
- Disintegration
- Effervescent
- Lozenges
- Chewable
- Sublingual and buccal
27
Describe disintegration tablets
Drug release: distintegration -> dissolution -> Drug absorption
Single disintegrating tablets can be prepared in the form of multilayers where incompatible drugs can be separated
28
Describe effervescent tablets
Drug release: dissolved in water -> disintegration -> dissolution -> drug absorption
CO2 formed when tablet is placed in H2O
Used to obtain rapid drug action (Aspirin) or facilitate the drug intake (vitamins)
Packed to protect from moisture
29
Describe lozenges
Dissolve slowly in the mouth and released drug dissolved in the saliva. It is used for local medication in the mouth/throat and no disintegrants are used
30
Describe chewable tablets
Used by patients who have difficulty in swallowing tablets; water not needed; mannitol is normally used as a base (low hygroscopy, pleasant and cooling sensation)
31
Describe sublingual (under the tongue) and buccal (between the gum and side of the cheek) tablets
used for drug release in the mouth for systemic uptake of the drug (rapid systemic effect without the first-pass metabolism)
Tablets are small and porous
32
Name the few tablet testing
- Uniformity of contents of active ingredients
- Disintegration
- Dissolution
- Mechanical Strength
33
How is uniformity of contents of active ingredients tested?
1. Weight uniformity test: Collect 20 tablets and determine the individual weight -> calculate the avg. weight and compare with that of the standard -> weight diff. should be in accepted range
2. Uniformity of active ingredients: Collect 10 tablets and determine the amt of drug in each -> Avg drug content of 10 tablets are calculated and the content of individual tablet should fall within given limits. At least 9 must assay within 15% of the declared potency and none may exceed 25%
34
How is disintegration tested?
Time required under a given set of conditions for a group of tablets to disintegrate into particles which will pass through a 10 mesh screen
Carried out using the disintegration tester - basket rack holding 6 plastic tubes immersed in a bath of suitable liquid held at 37C, preferably in a 1L beaker
35
How is dissolution tested?
| Dissolution is used to evaluate the release of drug substance from tablets - bioavailability
1. Stirred-vessel: Paddle method, rotating basket method - vessel filled with a dissolution medium with controlled volume and temperature
2. Continuous flow: preparation held within a flow cell where the dissolution medium is pumped through at a continuous rate
36
How is mech strength tested?
1. Attrition-resistance: friability (resistance to abrasion in shipping, packaging and handling) tests - tumbled and weighed to determine material lost
2. Fracture-resistance: Load on the tablet until it fracture along its diameter
37
What are the defects related to tabletting process
- Capping: due to air-entrapment in the granular material
- Lamination: due to air-entrapment in the granular material
- Cracking: due to rapid expansion of tablets when deep concave punchs are used
38
What are the defects related to excipient
- Chipping
- Sticking
- Picking
- Binding
- Problems due to excess binder/wet granules
39
What are the defects related to machine
- Double impression due to free rotation of the punches -> some engraving on the punch faces
- Mottling: due to a colored drug, improper mixing and dirt on punch faces
40
Name the types of tablet coating
- Film coating
- Sugar
- Press coating
- Functional coating - enteric, controlled-release
41
Describe film coating
- Deposition of a thin film of polymer surrounding the tablet core
- Polymer is dissolved into solvent and other additives like plasticiers and pigments are added. The resulting solution is sprayed into a rotated tablet bed/fluid bed and then put under drying conditions. After that, solvent is removed.
42
What are the process requirement of film coating?
1. Adequate means of atomizing the spray liquid for application to the tablet core
2. adequate mixing and agitation of the table bed
3. sufficient drying air to evaporate the solvent
4. good exhaust facilities to remove dust- and solvent- laden air
43
Describe sugar coating
1. Sealing: A resin separates tablet core from water used in coating formulation and adds strength to the core; e.g. shellac, cellulose acetate phthalate, polyvinyl acetate phthalate
2. Subcoating: weight increases 50 to 100%
3. Smoothing: filling the irregularity on the surface generated during subcoating - application of a syrup solution that contains pigments, starch, gelatin, acacial opacifier
4. Color coating: Use simple syrup, containing dyes/pigments -> uniform appearance
5. Polishing: application of waxes in a polishing pan -> elegance and gloss
6. Printing - uses pharmaceutical grade printing inks for additional identification
44
Describe press coating
Compaction of granulated materials around an already performed core using compressing equipment
45
Describe functional coatings
Coatings that perform a pharmaceutical function - confer controlled/enteric release on the dosage form
46
Describe controlled-release coatings
Use polymers with restricted water solubility/permeability like modified acrylates, water insoluble cellulose (ethyl cellulose)
47
Describe enteric coating
Used to protect tablet core from disintegration in the acid environment of the stomach, prevent degradation of acid sensitive drug, prevent irritation of stomach.
Types of enteric layer systems: 1-layer, 2-layer
48
Definition of tablets
Solid preparations each containing a single dose of one/more active ingredients and obtained by compressing uniform volumes of particles
49
Tablets must fulfill a number of specifications
- Have the correct dose of the drug
- Consistent weight, size and appearance
- Controlled and consistent drug release - constant dissolution and disintegration
- Biocompatibility: No contamination/harmful excipients
- Mechanically stable to withstand fracture and erosion
- Chemically, physically and microbiologically stable on storage
- Elegant and acceptable by patients
- Packed safely
50
What affects the tabletting process
- Quality of powder
- Press design
- Press condition
51
Importance of tablet production via granulation
- Improve flowability
- Increase bulk density - die fill
- Improve homogeneity and reduce segregation
- Improve compression properties and compactability
- Ensure color homogeneity
- Affect the dissolution process for hydrophobic, poorly soluble drug: use fine particulate drug mixed with hydrophilic filler and a hydrophilic binder
52
Tablet production via direct compaction is mainly used for
- Soluble drugs which can be processed as coarse particles
| - Potent drugs (in mg quantity) which can be mixed with coarse excipients
53
Examples of disintegrants
Cross-linked PVP and modified starches
54
Importance of dissolution test
- Evaluate the potential effect of formulation and process variables on the drug availability
- Ensure that preparations comply with product specifications
- Indicate the performance of the preparation under in vivo conditions
- In vitro and in vivo dissolution data must correlate
55
What is mechanical strength?
Resistance of a tablet towards fracturing and attrition
56
Principle of tablet coating
Application of coating composition to moving bed of tablets with concurrent use of heated air to facilitate evaporation of solvent
57
Importance of tablet coating
- Improve taste
- Avoid drug irritation
- Avoid drug inactivation in the stomach
- Improve drug effectiveness
- Improve dosing interval
- Reduce influence of humidity
- Provide mechanical strength
- Prolong shelf life
- Improve product identity, appearance and acceptability
- Improve patient compliance
58
Materials used for film coating
- Solvents: water, alcohol, methanol, isopropanol, acetone
- Film formers (enteric/nonenteric): HPMC, MHEC, EC, HPC, povidone, PEG
- Colorants: iron oxide, titanium oxide, pigments, food colorants and natural coloring materials
- Misc components: flavors, sweeteners, surfactants, antioxidants, antimicrobials, etc
- Plasticizers: modify the physical properties of the polymer to make it more usable -> decrease film brittleness, ensure good coating; e.g. coconut oil, diethyl phthalate, castor oil, PEG 400, surfactants
59
Examples of enteric coating material
- Cellulose acetate phthalate
- Polyvinyl acetate phthalate
- Acrylate polymers: Eudragit (R)
60
Ideal properties of enteric coating material
- Resistance to gastric fluids
- Susceptible/permeable to intestinal fluid
- Compatibility with coating components and drug substrate
- Formation of continuous film on the tablet
- Nontoxic, cheap and ease of application
- Readily printed
