The Fundamental Difference: Disintegration vs. Dissolution
When you take an oral medication, it must get into your bloodstream to have an effect. This journey begins in the gastrointestinal (GI) tract. For solid dosage forms like tablets and capsules, two key processes must occur: disintegration and dissolution [1.4.5].
- Tablets, which are made by compressing powdered medication with various binders and fillers, must first disintegrate—or break apart into smaller granules [1.2.2, 1.4.6].
- Capsules consist of a shell (usually made of gelatin) that contains the medication in powder, granule, or liquid form [1.2.3]. The primary step for capsules is dissolution, where the outer shell dissolves, releasing its contents [1.4.1].
Because capsules only need their shell to dissolve, they often release their active ingredients more quickly than tablets, which must first mechanically break down [1.2.3, 1.4.1]. This initial step can be rate-limiting for tablets, meaning it controls the overall speed of absorption [1.3.6].
The Speed Advantage of Capsules
Generally, capsules are absorbed faster than tablets [1.2.6]. Their shells are designed to dissolve quickly in the digestive tract, allowing the medication inside to be readily available for absorption into the bloodstream [1.4.2, 1.5.7]. This can lead to a quicker onset of the medication's effects, which is particularly beneficial for pain relievers or antibiotics where rapid action is desired [1.4.1, 1.2.6].
Softgels and Liquid Gels: The Fastest Form
Softgels, a type of capsule containing liquid medication, are typically the fastest to be absorbed [1.2.7]. The active ingredient is already in a liquid state, which means the body can absorb it almost immediately after the gelatin shell dissolves [1.5.1]. Studies on ibuprofen, for example, have shown that liquid-filled capsules may start working in just over 20 minutes, compared to around 30 minutes for solid tablets [1.5.2].
Bioavailability: It's Not Just About Speed
Absorption speed is closely tied to bioavailability, which is the proportion of a drug that enters the bloodstream and is able to have an active effect [1.2.7, 1.3.8]. Capsules often have higher bioavailability than tablets [1.2.1, 1.2.4].
Tablets may sometimes break down unevenly or incompletely, which can reduce the amount of the drug that gets absorbed [1.2.4, 1.4.4]. In contrast, the contents of a capsule are released more predictably once the shell dissolves [1.4.1]. This higher absorption rate can make capsules slightly more effective in some cases [1.2.1].
Comparison Table: Tablets vs. Capsules
| Feature | Tablets | Capsules (including Softgels) |
|---|---|---|
| Absorption Speed | Slower; must disintegrate first [1.4.2] | Faster; shell dissolves to release contents [1.4.4]. Softgels are fastest [1.2.7]. |
| Bioavailability | Can be lower due to incomplete breakdown [1.2.9] | Generally higher; more of the drug enters the bloodstream [1.2.1, 1.6.8]. |
| Dosing Flexibility | High; often scored and can be split for adjusted doses [1.2.1] | Low; cannot be split, ensuring a full dose is taken [1.4.2]. |
| Taste | May have an unpleasant or bitter taste unless coated [1.2.4, 1.4.2] | Generally tasteless as the shell masks the medication's flavor [1.2.2, 1.4.4]. |
| Stomach Irritation | More likely to cause irritation in the GI tract [1.2.2, 1.4.4] | Less likely to cause irritation, but can sometimes cause nausea [1.4.2]. |
| Shelf Life | Generally longer and more stable [1.4.1, 1.4.2] | Shorter, as they can be sensitive to humidity and light [1.2.4, 1.4.1]. |
Factors That Influence Absorption for Both Forms
It's important to remember that the dosage form is just one piece of the puzzle. Several other factors can affect how quickly and effectively a drug is absorbed [1.3.1, 1.3.2]:
- Food: Some drugs are absorbed better with food, while others require an empty stomach [1.3.5]. Fatty foods, in particular, can slow down stomach emptying and delay drug absorption [1.3.6].
- Stomach Acidity (pH): The pH of your stomach and intestines affects a drug's ionization and solubility. Weakly acidic drugs are better absorbed in the stomach's acidic environment, while weakly basic drugs are better absorbed in the more alkaline small intestine [1.3.3].
- Excipients and Coatings: Inactive ingredients (excipients) in both tablets and capsules can influence dissolution [1.3.5]. Special coatings, like enteric coatings, are designed to delay dissolution until the medication reaches the small intestine, protecting it from stomach acid [1.3.5].
- Physiological Factors: A person's age, GI health (e.g., Crohn's disease), and metabolic rate can all impact drug absorption [1.3.1, 1.3.2].
Conclusion: Which is Better?
While capsules, and especially softgels, generally offer faster absorption and higher bioavailability, there is no single "better" option for everyone [1.4.1]. Tablets provide benefits like longer shelf life, lower cost, and the ability to be split for flexible dosing [1.2.3, 1.4.4].
The best choice depends on the specific medication, the need for rapid onset of action, and individual patient factors like swallowing ability and dietary restrictions [1.2.1]. For example, a patient needing quick pain relief might prefer a liquid gel, while someone on a long-term medication with a stable dose might be better served by a more affordable tablet. Always consult with a healthcare provider or pharmacist to determine the most appropriate form of medication for your needs [1.4.1, 1.6.3].
Authoritative Link
For more in-depth information on drug absorption, the MSD Manual provides a comprehensive consumer-level overview [1.3.5].
