Module 1 - Tablets

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Tablets Chapter - NIPER JEE Tutorials

Module 1

We will learn the following topics in this module:

Various dosage forms: Tablets, capsules, solution, emulsion, suspension, semisolids, parentrals, opthalmics, and aerosols.

In the part 1 of this module, we will learn the tablets.

1. Tablets

* Tablets are solid dosage form.

* Tablets are cheaper than capsules- capsules are costly due to filling process-filling process is slower than compression.

* Tablets have the highest dose precision and least content variability among all the oral dosage form.

* Lowest cost among all the oral dosage forms.

* Tablets are not suitable:

  • For drugs with low compression properties due to amorphous nature.
  • Drugs have poor wetting, slow dissolution, oxygen or water sensitive (most suitable formulation for these drugs are capsules).

2. Types and classes of tablets

Note: This part is important. Many questions are asked from this part in NIPER JEE each year.

Tablet ingested orally

Compressed tablets

Multiple compressed tablets

Repeat action tablets

Delayed action and enteric coated tablets

Sugar coated coated tablets

Film coated tablets

Chewable tablets

Compressed tablets: Standard uncoated tablets manufactured by compression method

Multiple compressed tablets:

Use: To produce repeat action or prolonged action tablets.

To separate incompatible substances.

Disadvantage: It shows unpredictable bioavailablity of drugs due to multiple layers.

Its action is dependent on gastric emptying.

Repeat action tablets: Core tablet made of shellac or enteric polymer. A second layer of drug is coated as sugar.

Use: Prolonged action dosage form.

Delayed action and enteric coated tablets

* Tablet release the drug in small intestine.

* Polymers insoluble at gastric PH of 4.

* Polymers soluble above PH range of 7-8 (in the small intestine).

* Esterase enzyme (in the intestine) breaks down ester linkages of the polymer chains.

* USP requirement for enteric coated tablets: All six tablets should remain intact for at least 30 min in simulated gastric fluid at 37o C+- 2 oC. If one or two tablets fail to disintegrate in intestinal fluid, the test is repeated on 12 additional tablets, not less than 16 out of 18 tablets must disintegrate completely.

Polymers used for enteric coating

Cellulose acetate phthalate (CAP)

Polyvinyl acetate phthalate

Hydroxypropyl methyl cellulose phthalate

Methacrylic acid co-polymer (eudragit)

Cellulose acetate butyrate (CAB)

Hydroxypropylmethyl cellulose succinate

Applications

* Suitable for formulation of drugs show gastric irritation such as Aspirin, strong electrolytes (NH4CL), and Naproxen.

* Suitable for formulation of drugs cause nausea and vomiting when come in contact with the stomach.

* Suitable for formulation of drugs degraded in the stomach such as Erythromycin

* Other drugs, intestinal antibacterials and intestinal vermifuges.

Sugar coated and chocolate coated tablets

Use of sugar coating: to separate incompatible ingredients in core and coating. Coating may be 50% of total tablet weight.

Application: multivitamin combinations


Film coated tablets

Film coating is alternative to sugar coating.

Polymers used:

Hydroxypropyl cellulose (HPC)

Hydroxypropyl methyl cellulose (HPMC)

Methylcellulose (MC)

Ethylcellulose (EC)

Hydroxyethyl cellulose (HEC)

Povidone

PEGs

Enteric polymers:

Polymethyl acrylates

Cellulose acetate pthalate

Chewable tablets

Applications: Infants and elderly

Not suitable for bitter tasting drugs.

Ideal for the formulation of drugs have large doses such as antacids.

Formulation aspects:

Sweetening agents used: Mannitol and lactose

Flavoring agents used: Citric acid, grape, raspberry, lemon and cherry flavor

Diluents used: Mannitol, lactose, sucrose and sorbitol

Testing of chewable tablets

Dissolution testing same as for regular tablets.

USP apparatus 3- reciprocating cylinder for dissolution testing.

The test is modified by addition of glass beads.

Tablet used in the oral cavity

Buccal and sublingual tablets

Troches and Lozenges

Dental cones

Buccal and sublingual tablets

Buccal tablets:held between and cheek and teeth

Sublingual tablets: beneath the tongue

Advantage: first pass metabolism is bypassed and a rapid systemic action.

Formulation aspects:

Bland tasting excipients should be used to prevent saliva formation.

These tablets should not disintegrate rapidly in the mouth rather they should dissolve slowly for 15-30 minutes for absorption from the oral mucosa.

Applications:

Vasodilators

Steroids and hormones

Tests

16 out of 18 tablets should disintegrate within 4 hours

Troches and Lozenges

To have a local action in the mouth or throat-don't disintegrate in the mouth-dissolve slowly in the mouth for 30 minutes.

Manufacturing

Lozenges-compression and candy molding process

Troches- Compression methods

Dental cones

To be placed in the empty socket after tooth extraction.

Application: to release antibacterials, astringents and coagulants.

Vehicles of the tablets: Sodium bicarbonate, sodium chloride and amino acids

They dissolve slowly over a 20-40 minutes in extraction sites.

Tablet administered by other routes

Implantation tablets

Vaginal tablets

Implantation tablets

* For subcutaneous implantation.

* Provide sustained release effect for one month or a year.

* These tablets are cylinderic or rosette shaped and not more than 8mm in length.

* A special device called Kern injector is used to place the implantation tablets subcutaneously.

* Used to administer hormones.

Vaginal tablets

* For local and systemic action.

* Generally pear or ovoid shaped.

* The liver can be bypassed through this mode of drug delivery, thus prevention of drug destruction.

* Vaginal absorption follows first order kinetics.

* Most commonly used for vaginal infections.

Tablet used to prepare solutions

Efferevescent tablets

Dispensing tablets

Hypodermic tablets

Tablet triturates

Effervescent tablets

Prepared by mixing API with organic acids and sodium bicarbonate.

The effervescent powders were popularly called Seidlitz Powders.

Effervescent tablets release carbon dioxide when dropped in water.

Reaction:

Organic acid+sodium bicarbonate= sodium salts of acid+CO2+water

Reaction is completed- in less than one minute

Examples: Aspirin and cathartics

Formulation aspects: all the ingredients must be soluble in water.

Acid Sources

Citric Acid

Tartaric Acid

Malic Acid

Fumaric Acid

Adipic and Succinic Acids

Carbonate Sources

Sodium Bicarbonate

Sodium Carbonate

Potassium Bicarbonate and Potassium Carbonate

Sodium Sesquicarbonate

Sodium Glycine Carbonate

Binders

Binders such as Cellulose gums, gelatin, and starch paste not used in effervescent tablets due to their slow solubility and high residual water content

Dry binders: lactose, dextrose, and mannitol are preferred

Packaging of effervescent tablets

Hermetic type foil pouches

Stack packed in cylinderic tubes

Dispensing tablets

Are less commonly used today. They are added to the given volume of water to produce a solution of known concentration of drug.

Hypodermic tablets

They are used to prepare solution of drugs for injections.

Less commonly used today due to chances of non-sterile solution and risk of introduction of dust particles.

Tablet triturates

These are rarely used today. These are tablets prepared extemporaneously by a pharmacist.

Application: used for potent drugs.

References and further reading

Banker, G. S., & Anderson, N. R. (1991). The theory and practice of industrial pharmacy; Lachman, L. 3rd edition.

Herbert Lieberman, Leon Lachman, Joseph B. Schwartz (1989). Pharmaceutical Dosage Forms: Tablets, Volume 1, Second Edition.

Remington, J. P. (2006). Remington: The science and practice of pharmacy (Vol. 1). D. B. Troy, & P. Beringer (Eds.). Lippincott Williams & Wilkins.

About the Author

Kapil Pal's picture
Author: Kapil Pal

Kapil Pal holds a Bachelor's and Master's degree in Pharmacy. He is a registered pharmacist based in India. He had earned a national scholarship to study at the prestigious National Institute of Pharmaceutical Education and Research, Punjab, India. He has a lot of medical articles to his credit, published in the Drug Today Medical Times, India. He authored three chapters for the Encyclopaedia on Pharmacology and Society, Sage Publications, which is currently in the publishing stage. He has also published many business cases in Sage Publications.He has also authored a book on Ebola Virus Disease, titled Ebola: Is There Any Cure? He is currently working in a UK based pharmaceutical consultancy company.

Connect with Kapil Pal at: kapilpal1561988@gmail.com

http://www.pharmainfo.net/Kapil-Pal

 

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