molded tablets

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MOLDED TABLETS

Tablets:

Tablets Introduction Tablet : It is a solid unit dosage form of the medicament or medicaments with or without diluents and may be prepared by the molding or compression method. Types of tablets : 1. Molded tablets 2. Compressed tablets 2

Molded tablets:

Molded tablets 3

Molding techniques:

Molding techniques Compression molding : moistening the powder blend with a hydro alcoholic solvent followed by compressing into mold plates to form a wetted mass, which is, then air dried to remove the solvent Heat molding : A molten matrix in which drug is dissolved or dispersed can be directly molded into tablets Molding by vacuum evaporation : This process involves evaporation of solvent from a drug solution or suspension at a Standard pressure 4

Ingredients:

Ingredients Diluent Binder and adhesive Disintegrents Lubricants and glidants Colouring agents Flavoring agents Sweetening agents Antioxidants 5

Formulation :

Formulation Molded tablets – soluble ingredients, excipient or bases of lactose, dextrose, sucrose, mannitol , or other rapidly soluble materials or mixtures of these ingredients To insure rapid solubility of the soluble tablets, the excipients are passed through a fine screen or 120-mesh bolting cloth . 6

Formulation:

Formulation After the excipients are blended with the drug, the powder mix is moistened with the solvent, i.e., aqueous alcohol Other volatile solvents-acetone or hydrocarbons Antioxidants, such as sodium bisulphite, and buffers 7

HAND MOLDING:

HAND MOLDING 8

  Hand molding :

Hand molding Molds - metal Cavity plate- holes Peg plate - pegs. Typical die plate cavity sizes are 60 mg and 100 mg. Volume of the cavities constant Weight of the tablet - nature of the material. Cavity plate- pressed onto the peg plate Cavity plate falls, tablets pushed to the top of the plate Tablets are left on the pegs until they dry 9

Machine Molding:

Machine Molding 10

Machine Molding:

Machine Molding Mold plate- contains 4 sets of die holes 4 different positions Packing spinner- uniformly packs the mass Smoothening spinner-smoothens top surface of tablets Rake off- excess powder is removed Ejection-ejected onto conveyer belts Removal of solvent bye air dryer at 100 to 120 0 F for 1hr 11

Machine Molding:

Machine Molding 12

Defects In Molded Tablets:

Defects In Molded Tablets Related to solvent: Too little solvent- soft tablet Too much solvent-tablet shrinkage Aqueous alcoholic mixture: Poor water content-tend to powder and wear on edges High water content –harder and less soluble Related to drying: Solvent mediated migration of drug 13

Compressed Tablet triturates:

Compressed Tablet triturates Tablet triturates - prepared compression tablet machines -flat face punches When solubility and clear solution are required, water soluble lubricants - prevent sticking to the punches Lactose - diluent 14

Evaluation of Molded Tablets:

Evaluation of Molded Tablets Content uniformity: 9 out of 10 tablets taken from a sample of 30 as determined by the content uniformity method lies within the range of 85.0 to 115.0% of label claim no unit is outside the range of 75.0 to 125.0% If two or three dosage units are outside the range of 85.0 to 115.0%but not outside the 75.0 to 125.0% range 15

Evaluation of Molded Tablets:

Evaluation of Molded Tablets Disintegration test The disintegration test for sublingual tablets is run in the USP disintegration apparatus without disks, using water at 37 ± 2°C. All six tablets should disintegrate completely within the time limit specified in the monograph . 16

Evaluation of Molded Tablets:

Evaluation of Molded Tablets Dissolution test For sublingual nitro-glycerine tablets where only small volumes of saliva is sufficient One method-individual tablet is placed on a Millipore filter (0.45 mm) in the upper chamber of a plastic Millipore Swinnex 25 filter holder One ml of water is flushed through the chamber at 30-sec intervals up to 2 min, and samples at each time interval are collected and assayed 17

Evaluation of Molded Tablets:

Evaluation of Molded Tablets Second method- designed specifically for nitro-glycerine A tablet is dropped into 5 ml of water purged with nitrogen to remove any oxygen, in a cell containing a rotating platinum electrode The system is operated until no further increase in reduction potential is observed. From the data, the amount of nitroglycerin in solution at any time interval is obtained 18

SPECIAL PROBLEMS WITH MOLDED TABLETS :

SPECIAL PROBLEMS WITH MOLDED TABLETS Mechanisms of Potency Loss: Nitroglycerin - liquid with a significant vapor pressure at ambient temperatures Nitroglycerin tablets lose potency in four ways: Loss to the atmosphere - evaporation Intertab1et migration Sorption by packaging materials Chemical decomposition 19

SPECIAL PROBLEMS WITH MOLDED TABLETS:

SPECIAL PROBLEMS WITH MOLDED TABLETS Evaporation: The vapour pressure of pure nitroglycerin, although it increases sharply with an increase in temperature, is equal to only about 10 - 4 x the vapour pressure of water Due to the minute levels of nitroglycerin in tablets, even this slight volatility is sufficient to result in significant losses in potency 20

Vapour pressure of pure nitroglycerin as a function of temperature :

Vapour pressure of pure nitroglycerin as a function of temperature 21

SPECIAL PROBLEMS WITH MOLDED TABLETS:

SPECIAL PROBLEMS WITH MOLDED TABLETS When nitroglycerin tablets are exposed to ambient air currents for a few days. Loss of nitroglycerin from conventional tablets spread in a monolayer and exposed to ambient (rv25°C) air currents 22

SPECIAL PROBLEMS WITH MOLDED TABLETS:

SPECIAL PROBLEMS WITH MOLDED TABLETS Intertablet Migration: Most of the loss in content uniformity occurs during the first 2 months after manufacture some tablets increase in potency while others decrease is a most unusual observation that is attributed to the phenomenon of capillary condensation 23

Mechanism For The Migration Effect :

Mechanism For The Migration Effect 24

  :

Sorption by packaging Nitroglycerin - volatile , great affinity for common packaging materials, Nitroglycerin tablets- suffer significant potency losses via sorption by the packaging Example : Conventional tablets strip packaged in an aluminium foil and low-density polyethylene laminate lost about 90% of their nitroglycerin to the package 25 SPECIAL PROBLEMS WITH MOLDED TABLETS

Packaging:

Packaging POLYMER TYPE CRYSTALLINITY ABSORPTION OF 25 0 C NITROGLYCERIN 37 O C Vinyl (I) amorphous 28.9 24.8 Vinyl (II) amorphous 25.6 20.8 Vinyl (III) amorphous 25.6 20.8 High density polyethylene(IV) Highly crystalline 0.030 0.028 low density polyethylene(V) Highly weak crystalline 3.0 2.3 Ionomer(IX) Essentially amorphous 0.81 0.89 26

SPECIAL PROBLEMS WITH MOLDED TABLETS :

SPECIAL PROBLEMS WITH MOLDED TABLETS Chemical Decomposition Chemical stability- problem with conventional nitroglycerin tablets, both PEG400 and povidone - stabilize content uniformity,- hydrolysis of nitroglycerin Both 1, 2~dinitroglycerin and 1,3-dinitroglycerin were present in the aged samples 27

SPECIAL PROBLEMS WITH MOLDED TABLETS:

SPECIAL PROBLEMS WITH MOLDED TABLETS Formulation Potency 37 o C Loss (%) 45 o C Conventional tablet (no stabilizer) 9 7 Stabilized tablet(1% Polyvinylpyrrolidone ) 17 36 Stabilized tablet (Polyethylene glycol) - 8 28

Stabilization of Content Uniformity:

Stabilization of Content Uniformity The addition of PEG 400 or 4000 at a weight ratio of glycol to nitroglycerin of 0.85 would stabilize the content uniformity. Conventional tablets show an increase in the content uniformity parameter of about 11% on aging, povidone-stabilized tablets and PEG-stabilized tablets show an increase of only 2 to 3%. 29

Stabilization of Content Uniformity:

Stabilization of Content Uniformity 30

Marketed molded tablets:

Marketed molded tablets 31

Conclusion :

Conclusion The drugs which undergoes first pass metabolism are not suitable for oral administration So, such type of drugs should be given perorally i.e., sublingual, buccal, parental,etc The drugs given sublingually have many advantages like rapid absorption, rapid onset of action, and no first pass metabolism Drugs which change in physical form due to high compression force for such drugs molding technique is most suitable 32

References:

References Lieberman ha, lachman l, and Schwartz jb , pharmaceutical dosage forms: tablets, volume 1, second edition, marcel dekker , 1989 pg no-334-351 Ansel , Howard C., Pharmaceutical Dosage Forms and Drug Delivery Systems, 5 th ed., Lea & Febiger , Philadelphia, 1990, pg no-160-169 Remington's Pharmaceutical Sciences, 18 th ed., Mack Publishing Co., Easton, Pa, 1990 pg no-1656-1659 Pikaljm , lukes al, vapor pressure of nitroglycerin in sublingual molded tablets, journal of pharmaceutical sciences, volume 65, issue 9, pg no-1278-1284 Fusari as, nitroglycerin sublingual tablets, journal of pharmaceutical sciences, volume 62, issue 12, pg no-2012-2021 Pikaljm , bibler ad, Rutherford b,polymer sorption of nitroglycerin and stability of moldednitroglycerin tablets in unit dose packaging, journal of pharmaceutical sciences, volume 66, issue 9, pg no-1293-1297

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