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Pharmaceutics PTCB Test Prep Aug 21st, 2019

What are Solid Dosage Forms?

solid dosage forms

What are Dosage Forms?

As part of the PTCB exam, candidates are expected to have a thorough knowledge of medicine dosage forms. Here, we introduce what dosage forms are, as well as reviewing the details on solid dosage forms that you need to know.

Medicines are delivered to the body by a variety of forms. Some medicines are solids, such as tablets and capsules, and others are liquids, such as solutions and suspensions. These varying ways of delivering medicine to the body are called dosage forms.

More specifically, though, dosage forms encompass two combined elements:

  • The drug
  • The delivery system

In other words, how the drug is delivered to the body matters. When we talk about tablets, for example, they are not composed only of the “drug”. There are many other ingredients – called excipients -in the medicine that help it work.

Therefore, medicines are composed of the following two elements:

  • Active ingredient: the part of the medicine designed to treat the patient, also referred to as the ‘drug’.
  • Excipients: other ingredients that are added to the drug which, when combined, make the medicine. Excipients include preservatives, coloring agents, and stabilizers (also referred to as ‘inactive ingredients’, ingredients that do not possess any therapeutic qualities).

In other words, a drug and a medicine are not the same thing. The drug is the active ingredient, whereas the medicine is total between ‘drug + excipients’.

With these distinctions in mind, let’s turn our attention to one prominent dosage form class – namely, solid dosage forms.

Solid dosage forms include the following:

Solid Dosage Forms

  • Tablets
  • Capsules
  • Lozenge
  • Powders
  • Granules

Of course, not many medicines today are composed of powders and granules, though some are. Take inhaled medicines, for example. Beta-2 agonists, such as albuterol, need to be inhaled so that very fine drug particulates reach the bronchi of the lung.

Lozenges are hard medicines that dissolve slowly within the oral cavity. They are designed to prolong the effect of the medicine within its target site. For this reason, lozenges are used for their antiseptic, antitussive (cough suppressing), and mild anesthetic effects.

Below, we take a closer examination of tablets, capsules, and suppositories.

Tablets

Many drugs today are available as tablets. Tablets are one of the most common solid dosage forms and come with many different advantages, including:

  • Tablets are simple and convenient to use
  • Quickly and safely manufactured into convenient doses
  • Tablets are carried within portable packages, improving compliance
  • Tablets can be made to disguise unpleasanttastes from drug or excipients
  • Tablets can be easily identified by healthcare professionals – markings etc.
  • Tablets can be taken by patients themselves for added convenience

That said, there are numerous drawbacks of tablets. These include:

  • Not all drugs are suitable for oral use. Many drugs are degraded by stomach acid, such as insulin. However, some tablets are available as enteric-coated preparations to limit the damage of the low pH gastric environment.
  • Some drugs are deactivated by the liver, as the drug passes from the GI tract via the portal vein into the liver. This metabolism risk of the liver is referred to as the “first pass effect”.
  • Tablets may not be suitable when immediate therapy is required. After all, it takes time for tablets to be degraded by the GI tract, absorbed into the bloodstream, and delivered to the site of intended action.
  • Following on from the above, tablets are also not suitable in patients who are unable to swallow, either from disease or from loss of consciousness.
  • Some drugs are poorly absorbed by the GI tract. As a result, high doses need to be taken to ensure a therapeutic dose is reached. Higher doses can lead to greater and more unpleasant side effects.

Tablets are available in a wide variety of forms:

  • Chewable – nicely flavored, useful for children
  • Enteric-coated – coated to prevent acid destruction in the stomach
  • Sublingual – to be taken under the tongue
  • Buccal – to be taken inside the cheek
  • Film-coated – added protection, either from the sun, or to mask taste
  • Effervescent – granules dissolved in liquid to release carbon dioxide
  • Pellets – implanted beneath skin to prolong continuous drug absorption
  • Vaginal – inserted into the vagina to directly release drug to site of action

Tablets remain, then, the most popular dosage form prescribed by pharmacies.

Capsules

Capsules are one of the most popular dosage forms. There are two primary types:

  • Hard-shelled capsules. These capsules contain powder or power-like content. A smaller diameter half is filled and secured into a larger diameter half of the capsule.
  • Soft-shelled capsules. These are typically filled with oils or active ingredients that have been suspended or dissolved in oils.

Markings found on the capsule help to identify its size:

Size Volume (mL) Locked length (mm) External diameter (mm)
5 0.13 11.1 4.91
4 0.20 14.3 5.31
3 0.27 15.9 5.82
2 0.37 18 6.35
1 0.48 19.4 6.91
0 0.67 21.7 7.65
0E 0.7 23.1 7.65
00 0.95 23.3 8.53
000 1.36 26.14 9.91

Size 000 is generally too large to be taken by patients. Some capsule formulations are made so that the contents may be sprinkled on food.

Capsules have many of the same advantages of tablets:

  • Convenient to take, portable etc.
  • Easy to swallow
  • Due to the outer shell, capsules do not have an unpleasant taste
  • Easy to produce on mass scale

Let’s now turn our attention to suppositories.

Suppositories

Suppositories are one of those solid dosage forms applied to the rectum, vagina, or urethral tract. When inserted vaginally, and if intentionally shaped for vaginal use, they may also be known as inserts.

Suppositories are composed of an active ingredient within what’s called a suppository base. Examples of bases include:

  • Polyethylene glycol
  • Cocoa butter
  • Hydrogels
  • Glycerinated gelatin

This base, once it enters the body, dissolves in the heat and released the drug either locally or into the bloodstream for systemic effects. Suppositories should always be unwrapped before insertion. Pharmacy technicians should instruct their patients on how to correctly use suppositories.

Conclusion

During the PTCB exam, candidates are expected to have a thorough knowledge of dosage forms. Here, we’ve talked about solid dosage forms, but there are many other types of dosage form we have yet to examine. These include liquid dosage forms, semisolid dosage forms, and injectable dosage forms.

However, we encourage candidates for the PTCB test to study each section of their own, as opposed to exposing your time to too much detail. If you are already a registered member of PTCB Test Prep, you have access to our PTCB practice tests and questions.

When studying dosage forms, you need to bear the following 4 considerations in mind:

  • The advantages and disadvantages of each dosage form
  • Why one dosage form is preferred over another
  • How to counsel patients taking these types of dosage form
  • How each dosage form is manufactured

With these four criteria to hand, you neatly cover the type of detail expected on the PTCB examination.

Check back to our PTCB blog soon for more great content on dosage forms and other aspects of medicine that pharmacy technicians are expected to know. We help you pass the pharmacy technician exam – first time, every time.

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