Modified-release tablets are specialized dosage forms designed to alter the timing, rate, or location of drug release compared to conventional immediate-release tablets. These tablets enhance therapeutic efficacy, minimize side effects, and improve patient compliance.
1. Sustained-Release Tablets
Definition: Sustained-Release Tablets (SR Tablets) are a type of oral dosage form designed to release a drug slowly over an extended period of time. The primary goal of sustained-release tablets is to maintain a consistent drug concentration in the bloodstream over a longer period compared to immediate-release formulations. This helps in reducing the frequency of dosing and enhancing patient compliance.
Mechanism
• The drug is embedded in a matrix or coated with polymers that control its dissolution or diffusion.
Advantages
• Reduces the frequency of dosing.
• Maintains steady drug levels in the bloodstream.
• Improves patient compliance.
Examples
• Metformin SR: Used for type 2 diabetes.
• Theophylline SR: For asthma and chronic obstructive pulmonary disease (COPD).
2. Extended-Release Tablets
Definition: Extended-Release Tablets (ER Tablets) are a type of modified-release dosage form designed to release the drug gradually over an extended period, ensuring prolonged therapeutic effects with fewer doses. The aim is to provide steady drug levels in the body, minimizing fluctuations compared to immediate-release formulations.
Mechanism
• Incorporates polymers or osmotic systems that regulate the release rate.
Advantages
• Enables once-daily dosing.
• Reduces peak-trough fluctuations of drug levels.
Examples
• Venlafaxine XR: For depression and anxiety disorders.
• Propranolol ER: For hypertension and angina.
3. Fast-Dissolving Tablets (Orally Disintegrating Tablets)
Definition: Fast-Dissolving Tablets (FDTs) or Orally Disintegrating Tablets (ODTs) are solid dosage forms designed to disintegrate and dissolve rapidly in the mouth without the need for water. These tablets are particularly advantageous for patients who have difficulty swallowing (dysphagia) or require rapid onset of action.
Mechanism: Contains superdisintegrants such as crospovidone or croscarmellose that facilitate rapid disintegration.
Advantages
• Convenient for pediatric, geriatric, or dysphagic patients.
• Provides rapid onset of action.
Examples
Ondansetron FDT: For nausea and vomiting.
Risperidone ODT: For schizophrenia and bipolar disorder.
4. Multi-Layered Tablets
Definition: Multi-Layered Tablets are a specialized type of oral dosage form consisting of two or more layers of different drug formulations compressed into a single tablet. Each layer can contain the same or different active pharmaceutical ingredients (APIs) and excipients, allowing for controlled or sequential drug release.
Mechanism
• Each layer is formulated with specific excipients to achieve sequential or simultaneous release of APIs.
Advantages
• Allows combination therapies in a single tablet.
• Enables different release profiles for different layers.
Examples
• Ambien CR (Zolpidem): A two-layer tablet with immediate and extended-release layers for insomnia.
• Tramadol/Acetaminophen Combination Tablets: For pain relief.
5. Delayed-Release Tablets
Definition: Delayed-Release Tablets are a type of oral dosage form designed to release the active ingredient at a specific time or location in the gastrointestinal tract, rather than immediately after administration. The delay in drug release is achieved through the use of special coatings or formulations that respond to environmental triggers, such as pH or time.
Mechanism
Uses enteric coatings that dissolve in the alkaline pH of the intestine.
Advantages
• Protects drugs sensitive to stomach acid.
• Prevents gastric irritation from the drug.
Examples
• Pantoprazole DR: A proton pump inhibitor for acid reflux.
• Mesalamine DR: For inflammatory bowel diseases like ulcerative colitis.
6. Controlled-Release Tablets
Definition: Controlled-Release Tablets are oral dosage forms designed to release the active pharmaceutical ingredient (API) at a predetermined rate, maintaining consistent drug levels in the bloodstream over an extended period. The objective of controlled-release formulations is to improve therapeutic efficacy, reduce dosing frequency, and minimize side effects.
Mechanism
Often uses matrix systems or osmotic pumps.
Advantages
• Provides predictable drug release kinetics.
• Reduces dosing frequency and side effects.
Examples
• Methylphenidate CR: For attention deficit hyperactivity disorder (ADHD).
• Diltiazem CR: For hypertension and angina.
7. Matrix Tablets
Definition: Matrix Tablets are a type of oral controlled-release drug delivery system where the active pharmaceutical ingredient (API) is embedded within a polymer matrix. The matrix regulates the drug release by allowing it to diffuse or erode over time. These tablets are widely used to achieve sustained or controlled drug release profiles.
Mechanism
Drug diffuses or dissolves through the matrix material.
Advantages
Suitable for both sustained and extended-release formulations.
Examples
Metoprolol Matrix Tablet: For hypertension.
Carbamazepine Matrix Tablet: For epilepsy.
8. Effervescent Tablets
Definition: Effervescent Tablets are a type of solid dosage form designed to rapidly dissolve in water, releasing carbon dioxide and forming a fizzy solution that contains the dissolved active ingredient(s). This reaction is achieved by combining an acid (e.g., citric acid) and a base (e.g., sodium bicarbonate) within the tablet. Effervescent tablets are typically used for quick and complete drug absorption and for patient convenience.
Mechanism
Contains acid-base components (e.g., citric acid and sodium bicarbonate) that react to release carbon dioxide.
Advantages
• Enhances palatability.
• Improves absorption due to pre-dissolution of the drug.
Examples
• Vitamin C Effervescent Tablets: For supplementation.
• Alka-Seltzer: For heartburn and indigestion.
9. Chewable Tablets
Definition: Chewable Tablets are solid dosage forms designed to be chewed or dissolved in the mouth before swallowing. These tablets are formulated to be soft, pleasant-tasting, and easy to chew, making them ideal for individuals who have difficulty swallowing traditional tablets, such as children and elderly patients.
Advantages
• Easy administration.
• Mask unpleasant tastes.
Examples
Calcium Chewable Tablets: For osteoporosis prevention.
Montelukast Chewable Tablets: For asthma and allergies.
10. Buccal and Sublingual Tablets
Definition: Buccal and Sublingual Tablets are specialized oral dosage forms designed for absorption through the mucous membranes in the mouth, providing a faster onset of action than traditional oral tablets. These tablets bypass the digestive system and liver, which can reduce the first-pass metabolism of the drug.
Mechanism
Provides rapid absorption into the bloodstream, bypassing the first-pass metabolism.
Advantages
• Quick onset of action.
• Suitable for drugs that degrade in the gastrointestinal (GI) tract.
Examples
• Nitroglycerin Sublingual Tablets: For angina.
• Buprenorphine Sublingual Tablets: For opioid dependence.
11. Floating Tablets
Definition: Floating Tablets are a type of controlled-release oral dosage form that are designed to float on the surface of the stomach after ingestion. These tablets are formulated to have a low density, allowing them to remain buoyant in the gastric fluid, which results in prolonged drug release and extended therapeutic effects.
Mechanism
Contains gas-generating agents like sodium bicarbonate.
Advantages
• Prolongs gastric residence time.
• Enhances bioavailability of drugs absorbed in the stomach.
Examples
Ciprofloxacin Floating Tablets: For bacterial infections.
12. Osmotic Tablets
Definition: Osmotic Tablets are a type of controlled-release drug delivery system that uses osmotic pressure to regulate the release of the active ingredient from the tablet. These tablets are designed to release the drug at a controlled rate over a prolonged period, providing a steady and predictable release.
Mechanism
Water enters the tablet through a semi-permeable membrane, forcing the drug out through a laser-drilled orifice.
Advantages
• Precise and consistent drug release.
• Independent of gastrointestinal conditions.
Examples
• Glucotrol XL (Glipizide): For diabetes.
• Concerta (Methylphenidate): For ADHD.
Conclusion
Modified tablets cater to diverse therapeutic needs, providing flexibility in drug delivery systems. They enhance efficacy, minimize dosing frequency, and improve patient compliance, making them an integral part of modern pharmaceutical formulations.
