Pharmaceutics · Short notes

Tablets and Capsules: Short Notes & Cheat Sheet

Granulation, compression, coating, tablet defects, quality tests and hard and soft gelatin capsules.

Short notes

Read these before you attempt the topic's MCQs.

Wet granulation turns fine powder into free-flowing granules that compress well. Direct compression skips the granulating and drying steps.

Three routes: wet granulation, dry granulation (slugging or roller compaction) and direct compression.
Wet granulation improves flow and compressibility but is unsuitable for drugs sensitive to moisture or heat.
Dry granulation suits moisture-sensitive drugs such as aspirin.
Direct compression is the simplest and cheapest, but needs excipients that flow and compress well (e.g. microcrystalline cellulose, spray-dried lactose).
Compression happens in a die between an upper and a lower punch, on single-punch or rotary presses.

Sugar coating is traditional: sealing, subcoating, smoothing, colouring and polishing. It is slow and adds a lot of weight.
Film coating (e.g. HPMC) is thin, quick and adds little weight.
Enteric coatings (cellulose acetate phthalate, Eudragit L/S, HPMCP) resist stomach acid and dissolve in the intestine. They protect acid-labile drugs or the stomach itself.
Enteric-coated tablets must not be crushed or chewed.

Capping: the top of the tablet separates; lamination: the tablet splits into layers. Both are caused by trapped air, too many fines or too much pressure.
Picking and sticking: material sticks to the punch faces. It is usually caused by too little lubricant or too much moisture.
Mottling: uneven colour. Chipping and cracking are caused by worn tooling or brittle granules.
Weight variation is caused by poor flow of granules into the die.

Tests include weight variation, content uniformity, hardness (crushing strength), friability, disintegration and dissolution.
Friability is tested in a Roche friabilator (100 revolutions); weight loss should usually be no more than 1%.
Pharmacopoeial disintegration times: uncoated tablets within 15 minutes, film-coated within 30 minutes (BP). Enteric-coated tablets must survive acid and then disintegrate in buffer.
Hard gelatin capsules come in sizes 000 (largest) to 5 (smallest) and hold powders or pellets.
Soft gelatin capsules hold liquids or oils and are plasticised with glycerin or sorbitol.
Gelatin capsules are unsuitable for very hygroscopic or aqueous fills, because these soften or dry out the shell.

High-yield facts in one place. Cover the right-hand column and test yourself.

Defect	Main cause
Capping	Entrapped air, excess fines, high pressure
Lamination	Air entrapment, rapid decompression
Sticking / picking	Too little lubricant, too much moisture
Mottling	Uneven distribution of colour or migrating dye
Weight variation	Poor granule flow into the die
Hard, slow tablets	Too much binder or compression force

Test	Measures / limit
Friability	Roche friabilator; loss ≤ 1%
Hardness	Crushing strength (Monsanto, Pfizer testers)
Disintegration	Uncoated ≤ 15 min, film-coated ≤ 30 min (BP)
Dissolution	USP apparatus 1 basket, 2 paddle
Content uniformity	Drug content of individual units
Capsule sizes	000 largest → 5 smallest

Capping = the Cap comes off: In capping the top of the tablet separates; in lamination it splits into layers.
Triple zero is huge: Capsule size 000 is the largest and 5 is the smallest.

Aspirin, being moisture-sensitive, is made by dry granulation (slugging), not wet granulation.
Friability measures resistance to abrasion; hardness measures resistance to crushing. They are different tests.
Sugar coating adds a lot of weight; film coating adds very little.
Soft gelatin capsules are for liquids and oils; hard capsules are for powders and pellets.

Attempt the Tablets and Capsules MCQs while the notes are fresh. Anything you get wrong is saved to your incorrect list for the next revision round.