Tablets are one of the most common forms of medication worldwide. They are easy to use, stable, portable, and can be designed in many different ways to control how fast, how long, or where the drug works in the body.

But you’ve probably seen tablets labeled as MR, SR, ER, CR, EC, ODT, and more — and wondered:

What do these labels mean? Why are there so many types? Which type is better?

This detailed guide explains the different types of tablets, how they work, and the differences between them in simple language.

1. Immediate Release Tablets (IR)

What they are

Immediate Release tablets are the most common type. They dissolve quickly in the stomach after swallowing, usually within 20–30 minutes.

How they work

The drug is released all at once, leading to:

Fast absorption
A quick rise in drug levels in the blood
Shorter duration of action

Common uses

Painkillers like ibuprofen, most antibiotics, vitamin supplements, and many over-the-counter drugs.

Who benefits

People needing rapid relief, such as in pain, fever, headaches, or acute infections.

2. Modified Release Tablets (MR)

What they are

“Modified Release” is an umbrella term. It simply means the tablet releases the drug in a way that is changed from the normal immediate release.

MR includes:

SR (Sustained Release)
ER (Extended Release)
CR (Controlled Release)
XR (Extended Release)
LA (Long-Acting)
PR (Prolonged Release)

Often MR = any system designed to slow down or control how the drug is released.

Why MR tablets exist

Some drugs work better and cause fewer side effects when released slowly and steadily, not all at once.

3. Sustained Release Tablets (SR)

What they are

SR tablets are designed to release the drug slowly over a longer period, usually 8–12 hours.

How they work

They reduce the number of doses needed per day.

Advantages

More stable blood levels
Fewer doses (twice daily instead of three or four)
Reduced side effects from high peaks

Limitations

Cannot be crushed or broken (risk of overdose)
Not suitable for drugs needing quick action

Example medications

SR metformin, SR diclofenac.

Simple explanation

SR = slow release over many hours.

4. Extended Release Tablets (ER or XR)

What they are

ER tablets release the medication gradually so one tablet lasts 12–24 hours.

Key point

ER usually lasts longer than SR.

Benefits

Once-daily dosing
Improved patient compliance
More consistent drug levels

Simple explanation

ER/XR = lasts the whole day.

5. Controlled Release Tablets (CR)

What they are

CR tablets are designed to control both the speed and timing of drug release.

They release medication at a specific rate, not just slowly.

Difference from SR/ER

SR: slow release
ER: long release
CR: precisely controlled release pattern

Examples

Some blood pressure meds, anti-depressants.

6. Delayed Release Tablets (DR)

What they are

These tablets release the drug after a delay, not immediately.

The delay protects the drug from stomach acid or protects the stomach from irritation.

How long is the delay?

Usually 1–2 hours until they reach the small intestine.

Simple explanation

DR waits until the tablet passes the stomach.

7. Enteric-Coated Tablets (EC)

What they are

Enteric coating stops the tablet from dissolving in the stomach.
It only dissolves in the intestine.

Why use EC tablets?

Protects stomach from irritating drugs (e.g., aspirin EC)
Protects drug from stomach acid (e.g., omeprazole EC)
Allows targeted intestinal release

Do not crush or chew an EC tablet.

Simple explanation

EC = stomach-safe, intestine-dissolving tablet.

8. Chewable Tablets

What they are

Designed to be chewed, not swallowed whole.

When used

For children
For people who can’t swallow tablets
For fast absorption (like antacids)

Examples

Antacids, some vitamins, pediatric medications.

Simple explanation

You chew before swallowing.

9. Effervescent Tablets

What they are

Tablets that dissolve in water, producing bubbles.

Advantages

Faster absorption
Gentler on the stomach
Good for people with swallowing difficulty

Examples

Vitamin C effervescent, electrolyte tablets.

15. Sugar-Coated Tablets

What they are

Coated with a layer of sugar.

Purpose

Improves taste
Masks smell
Protects drug inside

Downside

Makes tablet larger.

Simple explanation

Sweet coating for taste and protection.

16. Layered Tablets (Bilayer Tablets)

What they are

Tablets with two or more layers, often combining:

Immediate release
Sustained release

Example: A painkiller with fast pain relief + long-lasting relief in a single pill.

Simple explanation

Two tablets in one — fast + slow release.

17. Press-Coated Tablets

What they are

A tablet inside another tablet.

Used for:

Delayed release
Targeted intestinal release

Simple explanation

Tablet within a tablet for special timing.

18. Osmotic Pump Tablets (OROS Tablets)

What they are

Advanced tablets that use osmotic pressure to push drug out slowly through a tiny hole.

Benefits

Very precise control
Long-lasting (up to 24 hours)

Examples

Concerta (ADHD medication), some blood pressure meds.

Simple explanation

Water enters tablet → pushes drug out evenly.

19. Vaginal and Rectal Tablets (Pessaries and Suppositories)

Technically tablets, but used inside the body, not swallowed.

Uses

Antifungal treatments
Hormonal therapy
Laxatives (rectal tablets)

Simple explanation

Inserted, not swallowed — works locally or systemically.

20. Tablets for Targeted Release (Colon-Release, Gastric-Release)

These tablets release medicine only in:

Stomach
Small intestine
Colon

Used in:

Inflammatory bowel disease
Crohn’s disease
Ulcerative colitis

Simple explanation

Tablet releases medicine exactly where it’s needed.

Summary of Main Types (Simplified Table)

Type	Meaning	Release Speed	Example Purpose
IR	Immediate Release	Fast	Pain, fever
SR	Sustained Release	Slow (8–12 hrs)	Chronic conditions
ER/XR	Extended Release	12–24 hrs	Once-daily meds
CR	Controlled Release	Precise rate	Blood pressure, psychiatric meds
MR	Modified Release	Any non-immediate form	Various
EC	Enteric-Coated	Intestine only	Protect stomach
ODT	Disintegrating	Melts in mouth	Nausea, migraine
Chewable	Chew	Fast	Antacids, vitamins
Effervescent	Dissolve in water	Very fast	Vitamins, salts
Sublingual	Under tongue	Very fast	Angina
Buccal	Cheek	Slow & steady	Pain, addiction therapy

Practical Tips for Patients

Do NOT crush or break these tablets:

SR
ER / XR
CR
MR
OROS osmotic tablets
Enteric-coated (EC)

Crushing them can cause:

Sudden release → overdose
Stomach irritation
Loss of effectiveness

Safe to crush (in most cases):

Plain IR tablets
Some chewable or dispersible tablets

Always ask a pharmacist before crushing.

Conclusion

Tablets have evolved far beyond simple pills. Modern tablets can:

Release medicine quickly
Release it slowly
Release it only in certain parts of the gut
Melt in your mouth
Work instantly under the tongue
Work for an entire day with one dose

Understanding the differences between IR, SR, ER, CR, MR, EC, ODT, and others helps ensure safer and more effective use of medications.

Sources

U.S. Food and Drug Administration (FDA). “Extended-Release and Long-Acting Medications.”
European Medicines Agency (EMA). “Modified Release Oral Dosage Forms.”
Merck Manual Professional Edition — Drug Absorption and Formulations.
Pharmaceutical Dosage Forms and Drug Delivery Systems, 9th Edition.
American Society of Health-System Pharmacists (ASHP) — Medication Formulation Guidelines.
United States Pharmacopeia (USP) Drug Release Standards.