BP102T Unit 3 – Pharmaceutical Calculations & Principles
Unit 3 provides exhaustive coverage of liquid formulations: Monophasic systems (Simple Syrup IP 66.7% w/w, Elixirs, Linctuses, Gargles, Mouthwashes, Enemas) and Biphasic systems (Suspensions: Stokes' law, flocculation vs deflocculation, sedimentation volume; Emulsions: O/W vs W/O, Bancroft's rule, HLB system, identification tests, and physical instability phenomena).
📋 Prescribed Syllabus Topics
📖 Detailed Lecture Notes & Solved Examples
11. Monophasic Liquid Dosage Forms: Syrups, Elixirs & Gargles
Dedicated Webpage➔A monophasic liquid is a true, homogeneous, single-phase solution where solute molecules are uniformly dispersed at the molecular level within a solvent. Simple Syrup IP is a saturated solution of sucrose in purified water containing 66.7% w/w (equivalent to 85% w/v in USP). High sucrose osmotic pressure prevents microbial and fungal growth without adding chemical preservatives. Elixirs are clear, sweetened hydro-alcoholic liquids (alcohol content 4% to 40%) used for formulating water-insoluble drugs (e.g. Phenobarbital elixir). Linctuses are viscous oral liquids prescribed for demulcent cough relief. Gargles and mouthwashes are aqueous oral cavity antiseptics.Monophasic ka matlab single phase wala liquid solution. Simple Syrup IP me 66.7% w/w cheeni (sucrose) hoti hai. Itni high sugar concentration bacteria ke andar se paani kheench leti hai (Osmosis), isliye isme preservative nahi dalna padta. Elixirs me water-insoluble dawaiyon ko gholne ke liye alcohol (4-40%) milaya jata hai.
▶Formulation of Simple Syrup IP (66.7% w/w)
Standard preparation method using official pharmacopoeial proportions.
| Monophasic Liquid | Vehicle / Base | Key Additives | Clinical Purpose |
|---|---|---|---|
| Simple Syrup IP | Purified water (66.7% w/w sucrose) | Flavoring agents, coloring dyes | Sweet vehicle for bitter pediatric drugs; self-preserving |
| Elixir | Hydro-alcoholic (Water + Ethanol) | Glycerin, Propylene glycol, Sorbitol | Solubilizes water-insoluble drugs (e.g., Antihistamines) |
| Linctus | Viscous syrup / glycerin base | Demulcent soothing agents | Soothes irritated pharyngeal mucosa to suppress dry cough |
| Gargle | Aqueous solution (diluted before use) | Phenol, Potassium chlorate, Thymol | Antiseptic treatment of throat infections (tonsillitis) |
| Mouthwash | Aqueous / Hydroalcoholic with surfactant | Chlorhexidine, Cetylpyridinium chloride | Oral hygiene, anti-plaque, reducing halitosis |
- •Simple Syrup IP concentration: 66.7% w/w (Self-preserving due to high osmotic pressure).
- •Simple Syrup USP concentration: 85% w/v (equivalent to 64.7% w/w, specific gravity ~1.313).
- •Elixirs contain ethanol (4-40%) to solubilize non-polar active ingredients.
- •Gargles are concentrated solutions intended to be diluted with warm water before treating pharyngitis/tonsillitis.
22. Biphasic Suspensions: Stokes' Law, Flocculated vs Deflocculated Systems
Dedicated Webpage➔A pharmaceutical suspension is a coarse, heterogeneous dispersion where insoluble solid drug particles (dispersed phase, size 0.5 to 5.0 μm) are uniformly distributed throughout a liquid vehicle (continuous phase). The sedimentation velocity of particles is governed by Stokes' Law ($v = \frac{2r^2(\rho_s - \rho_0)g}{9\eta}$). Suspensions are classified into Flocculated systems (particles form loose, porous aggregates that settle rapidly but redisperse instantly upon shaking without caking) and Deflocculated systems (particles settle slowly as individual units, but form an irreversible, hard, compact cementitious 'cake' at the container bottom).Suspension me aghulansheel (insoluble) powder liquid me tairta rehta hai. Stokes' Law ke hisaab se agar particle size chhota kar dein aur liquid ki viscosity badha dein, toh powder dheere baithega. Flocculated suspension sabse achha hota hai kyunki isme powder neeche baithne ke baad bottle hilate hi wapas ghul jata hai aur pathar jaisa caking nahi banata.
▶Stokes' Law Mathematical Formulation & Parameter Optimization
Formula for settling velocity: $v = \frac{d^2(\rho_s - \rho_0)g}{18\eta}$
| Property | Flocculated Suspension | Deflocculated Suspension |
|---|---|---|
| Particle Association | Loose aggregates (flocs) with porous network | Individual, separate particles |
| Rate of Sedimentation | Rapid (flocs settle quickly) | Slow (individual tiny particles settle gradually) |
| Nature of Sediment | Loose, porous, easily redispersible with shaking | Hard, compact 'cake' that CANNOT be redispersed |
| Supernatant Liquid | Clear (particles settle into flocs together) | Turbid / cloudy (fine particles remain suspended) |
| Elegance / Appearance | Less elegant initially due to quick clear layer | Pleasing, uniform appearance for a longer duration |
| Preferred Clinical Choice | IDEAL formulation for commercial shelf-life | Avoided due to risk of irreversible caking |
- •Sedimentation Volume ($F$): $F = \frac{V_u}{V_0}$ (Ratio of ultimate settled volume $V_u$ to original suspension volume $V_0$. For an ideal flocculated suspension, $F \approx 1.0$).
- •Degree of Flocculation ($\beta$): $\beta = \frac{F}{F_\infty} = \frac{(V_u / V_0)_{\text{flocculated}}}{(V_u / V_0)_{\text{deflocculated}}}$.
- •Suspending Agents: Tragacanth (0.2-1.0%), Sodium CMC (0.5-2.0%), Veegum (Magnesium Aluminum Silicate).
33. Biphasic Emulsions: Types, HLB System, Identification Tests & Instabilities
Dedicated Webpage➔An emulsion is a thermodynamically unstable biphasic system consisting of at least two immiscible liquid phases (usually water and oil), one of which is dispersed as fine globules (internal phase) throughout the other (external continuous phase), stabilized by an Emulsifying Agent (emulgent). Bancroft's Rule states that the phase in which the emulsifier is most soluble becomes the continuous external phase. The Hydrophilic-Lipophilic Balance (HLB) scale (0 to 20, established by Griffin) guides emulsifier selection.Emulsion tel aur paani ka mixture hota hai jise stable rakhne ke liye Emulsifying agent (Tween, Span) milate hain. O/W emulsion me tel ki boondein paani me hoti hain, aur W/O me paani ki boondein tel me hoti hain. Iski pehchan 4 tests se hoti hai: Dilution test, Dye test, Conductivity test aur Fluorescence test. Cracking ka matlab hai emulsion ka poori tarah toot jana.
▶Emulsion Type Identification Tests (O/W vs W/O)
Four laboratory methods to determine emulsion type.
| Instability Type | Reversibility | Physical Mechanism | Corrective Action |
|---|---|---|---|
| Creaming | Reversible upon gentle shaking | Density difference causing oil to rise to top | Homogenize to reduce globule size, increase vehicle viscosity |
| Flocculation | Reversible | Weak van der Waals attraction between globules | Optimize zeta potential using appropriate surfactant concentration |
| Coalescence | Irreversible | Interfacial film ruptures, globules fuse | Use stronger multi-molecular or viscoelastic emulsifier film |
| Cracking (Breaking) | Strictly Irreversible | Complete destruction of emulsifier film; separate layers | Reformulate batch with compatible HLB emulsifier blend |
| Phase Inversion | Reversible/Irreversible | O/W flips to W/O due to phase volume > 74% or electrolyte addition | Control phase volume ratio (< 74%) and temperature |
- •Oil-in-Water (O/W): Oil globules dispersed in water continuous phase (Oral emulsions like Castor oil emulsion, washable creams).
- •Water-in-Oil (W/O): Water droplets dispersed in oil continuous phase (Cold creams, oily liniments for prolonged moisturizing).
- •HLB System (Griffin): HLB 3-6 -> W/O Emulsifiers (Span 80); HLB 8-16 -> O/W Emulsifiers (Tween 80).
- •Physical Instabilities: Creaming (reversible upward/downward movement), Flocculation (aggregation without coalescence), Coalescence (globules fuse together), Cracking/Breaking (irreversible complete phase separation), Phase Inversion (O/W switches to W/O).
- In 10-mark questions on Emulsions, explain all 4 Identification Tests (Dilution, Dye, Conductivity, Fluorescence) with neat diagrams.
- State the mathematical formula for Stokes' Law and explain 3 industrial formulation methods to retard sedimentation.