INTRODUCTION:

In the novel drug delivery system, a drug is delivered at a rate determined by the needs of the body during the duration of treatment, and its active ingredients are delivered to the site of action. Currently, no drug delivery system can fulfill all the lofty goals, however, sincere efforts are being made to achieve them through novel approaches to drug delivery¹.

Different routes of administration are available for controlled and targeted drug delivery, resulting in a variety of novel drug delivery systems. In recent years, there has been considerable interest in using microspheres for drug delivery². In terms of sustained or controlled release, microspheres of biodegradable and nonbiodegradable polymers have been studied. Microspheres are characterized by a microphase separation morphology, which acts as a catalyst to control degradation rate and drug release³.

Methods for preparation of microspheres:

The following techniques were adopted in making microspheres^4,5:

1. Single emulsion techniques

2. Double emulsification techniques

3. Polymerization

a. Normal polymerization

· Bulk

· Suspension

· Emulsion

b. Inter-facial polymerization

4. Coacervation phase septation technique

5. Spray drying and spray congealing technique

6. Solvent evaporation method

7. Solution- strengthening distribution method

8. Wax coating and Hot-melt method

Pharmaceutical application of microspheres

The main inputs of microspheres in pharma field are as follows⁶.

· Vaccine delivery

· Monoclonal antibodies

· Imaging

· Topical porous microsphere

· Nasal drug delivery

· Oral drug delivery

· Targeting drug delivery

· Gastro-retentive controlled delivery system

· Bio-medical applications

· Pharmaceutical application

Advantages of microspheres:

Microspheres have these merits⁷

· Microspheres show constant and long-lasting therapeutic action.

· Dosing frequency can be changed, and so we can improve patient compliance.

· Due to their spherical shape and smaller size, they could be injected into the body.

· good bioavailability and low risk of side effects

· Microsphere morphology all depends on controllable variability in degradation and drug release.

Disadvantages of microspheres:

The demerits of microspheres are as follows⁸

· The modified release from the formulations

· The release rate of the controlled release dosage form may vary due to a variety of factors, like food and the rate of transit through the gut.

· differences in the release rate from one dose to another.

· Controlled release formulations generally contain a higher drug load and, thus, any loss of integrity of the release characteristics of the dosage form may lead to potential toxicity.

· Dosage forms of this kind should not be crushed or chewed.

For quick reference to the researchers who want to work on microspheres, Table 1 summarizes previous successful attempts on microspheres.

Table 1: Past work done on drugs and polymers in making microspheres

Drug	Polymer	Reference
Doxorubicin	Poly lactic acid (PLA)	⁹Juni et al., 1985
Diclofenac sodium	Albumin	¹⁰Hideshi et al., 1990
5-fluro uracil	PLA, and Polyglycolide (PGA)	¹¹Moritera et al., 1991
Methotrexate	Poly anhydride (PA)	¹²Bhagat etal., 1994
Ofloxacin	Gelatin, poly glycolic acid-co-DL-lactic acid (PGLA)	¹³Habib et al., 1999
Bupivacaine	PLA, and PLGA	¹⁴Kwak et al., 2000
Naltrexone	PLA	¹⁵Dinarvand et al., 2003
Metaprolol tartrate	Egg albumin, ethyl cellulose (EC), and Eudragit RL 100	¹⁶Rajinikanth et al., 2003
Cyclosporin A	PLA, and PLGA	¹⁷B Malaekeh et al., 2005
Ciprofloxacin	Chitosan, and Pectin	¹⁸Orhan et al., 2006
Glibenclamide	Mucuna gum	¹⁹Amaechi et al., 2007
Diltiazem	Polyethylene glycol 600	²⁰Nappinnai et al., 2007
Meloxicam	Poly lactic acid	²¹Im et al., 2008
Ketorolac tromethamine	Polycaprolactone (PCL), and PLA	²²Sinha et al., 2008
NNMDA-curcumin	PCL	²³Sankavarapu et al., 2009
Theophylline, xanthine derivative	PCL	²⁴Jelvehgari et al., 2010
Tinidazole	Bovine serum albumin	²⁵Parashar et al., 2010
Aceclofenac	PLA	²⁶Chandiran et al., 2010
Zopiclone	PCL	²⁷Swapna et al., 2010
Idarubicin	EC, and HPMC	²⁸Ganesh et al., 2010
Famotidine	Carboxy Methyl Cellulose	²⁹Arya et al., 2010
Loxoprofen	EC	³⁰Venkatesan et al., 2011
Theophylline	Chitosan, sodium alginate, and egg albumin	³¹Jelvehgari et al., 2011
Tetanus toxoid	Chitosan	³²Arthanari et al., 2011
Caffeine	Bovine serum albumin	³³Malviya et al., 2011
Methotrexate	PLGA	³⁴Sibeko et al., 2012
Ibuprofen	poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), and PLA	³⁵Bazzo et al., 2012
Ropinirole HCl	PLGA	³⁶Madan et al., 2013
Infliximab	PLGA	³⁷Gokhale et al., 2013
Enalapril maleate	Egg albumin	³⁸Nanjwade et al., 2014
Aspirin	EC	³⁹Reddy et al., 2014
Isoniazid	Hydroxyethyl methacrylate (HEMA)	⁴⁰Jafari et al., 2015
Lovastatin	PLA	⁴¹Guan et al., 2015.
Indomethacin	Egg albumin, EC, and Eudragit L 100	⁴²Bose et al., 2016
Mefenamic acid	Ethyl cellulose	⁴³Anusha et al., 2016
Venlafaxine HCl	Chitosan	⁴⁴Jain et al., 2016
Ropivacaine	Chitosan	⁴⁵Ni et al., 2016
Simvastatin	PLGA	⁴⁶Masaeli et al., 2016
paracetamol	chitosan-graft-polyacrylamide (CS-g-PAM)	⁴⁷Bulut et al., 2016
Nateglinide	Olibanum gum, Guar gum (GG), and sodium alginate	⁴⁸Pandey et al., 2016
Insulin	HEMA	⁴⁹Kenechukwu et al., 2016
Losartan potassium	EC	⁵⁰Khairnar et al., 2017
Azithromycin	Xanthan gum, and GG	⁵¹Bhattacharjee et al., 2018
Ivabradine HCl (IBH)	Egg albumin, and EC	⁵²Singh et al., 2019
Metformin hydrochloride	Khaya gum, and sodium alginate	⁵³Ozoude et al., 2020
Pentazocin	EC	⁵⁴Jabar et al., 2021
Ranitidine	Carbopol 934, chitosan and sodium alginate	⁵⁵Palanivelu et al., 2021

CONCLUSION:

Microsphere has the advantage of target specificity and better patient compliance compared to many other types of drug delivery systems. From the foregoing, it is concluded that microspheres are a promising candidate for sustained and targeted drug delivery in various targeted organs. Aside from drug delivery, microspheres are also used for imaging tumors, detecting biomolecule interactions for diagnostics, and cancer treatment, among other things. Therefore, in the future, microspheres will play a very important role in the advancement of medicine. Researchers will be provided with a quick reference to past literature on microspheres through this review.

ACKNOWLEDGMENTS:

The authors are thankful to the college management for the encouragement and the support.

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Received on 03.02.2022 Modified on 18.02.2022

Res. J. Pharma. Dosage Forms and Tech.2022; 14(3):245-248.

DOI: 10.52711/0975-4377.2022.00040

Methods for preparation of microspheres:

The following techniques were adopted in making microspheres4,5: