[0:12]this lecture series on pharmaceutics. Pharmaceutics is defined as the branch of pharmacy that deals with turning a chemical entity into a dosage form.
[0:22]So let's say that you've discovered a chemical, chemical X. It's a great chemical which cures lung cancer. However, at this stage it's just a chemical in a beaker and it's kind of useless.
[0:37]Which is why you need pharmaceutics to convert this chemical into an appropriate dosage form. In order to do that, you need to study chemical X's physical and chemical properties, things like log P, its molecular weight, its melting point, etc.
[0:56]After that, you want to formulate the drug into an appropriate dosage form, and there are many dosage forms to choose from. Should your drug be a capsule? Should it be in an IV bag? Should it be an inhaled aerosol?
[1:13]These criteria are dictated by pharmaceutics, which is governed by LADME.
[1:22]LADME stands for liberation, absorption, distribution, metabolism, and excretion.
[1:30]Liberation is the release of the drug from its dosage form. Let's say you swallowed a solid tablet. It has to solubilize into a liquid before it can go anywhere.
[1:39]A is for absorption. There are three general types of absorption: paracellular, which is absorption of the drug between cells, transcellular, which is the absorption of the drug across the cell, or the absorption of the drug via transport proteins.
[1:57]Okay, so the drug is now liberated into solution and absorbed transcellularly into the intestines. Next, it has to be distributed to the target site, and that usually occurs via the circulation.
[2:12]Next is metabolism, which is usually hepatic, meaning via the liver, and that's my attempt at drawing the liver. Anyway, so liver enzymes convert the active drug into its inactive form to prepare it for elimination.
[2:27]Elimination of the drug is either fecal, renal, or pulmonary.
[2:34]As mentioned earlier, there are many types of dosage forms. A dosage form is like a car which transports the passenger, aka the drug, into its target.
[2:44]Ideally, a dosage form is comfortable, stable, easy to use, and comes in a manageable size unit. After all, no one wants to be swallowing a giant pill.
[2:59]For oral drug delivery, or enteral delivery, meaning GI, so anything that's enteral means that it goes through the gastrointestinal tract. There are tablets, capsules, liquids, granules, to name a few.
[3:13]It's the most common route of administration. However, it wouldn't be suitable for some patients who are vomiting or convulsing. Parenteral dosage forms are administered outside the gastrointestinal tract, and they range from injectables to ophthalmic eye drops, all of which have to be sterile.
[3:34]Injectable routes can include IVs, so intravenous, intramuscular, and subcutaneous, which goes into the fatty areas like the arms, thigh, and abdomen.
[3:46]Dermal drug delivery includes dosage forms like ointments, creams, and gels. Transdermal patches are like a sticker with a gel matrix containing the drug.
[4:00]So the gel matrix releases the drug into the systemic circulation over a prolonged period of time.
[4:07]Other dosage forms include suppositories, which go into the rectum, and they actually avoid being metabolized by the liver and are useful in patients who can't take tablets. Pessaries go into the vagina.
[4:23]Aerosol inhalers are like, you know, your typical asthma inhaler.
[4:30]All of the above dosage forms are either solids, solutions, colloids, or suspensions, and those will be discussed in further detail in future videos.
[4:39]So we have all these dosage forms and routes. The choice of route of administration really depends on things like the condition, convenience, amount of drug required, potency, onset of action, and disease state.
[4:56]So, the condition itself, if it were an eye infection, for example, it would be more rational to formulate an eye drop versus a tablet.
[5:05]Convenience, it's more convenient to take a tablet than to use an injection. Potency, it's the amount of drug required to do an action.
[5:15]So, for example, if we had two drugs, one required one gram to work, and the other required 25 grams to work for the same effect, the one gram drug is said to be more potent because we need less of it.
[5:29]Onset of action. If we have a patient who is systemically ill in a hospital, an IV is more suitable because it will have an onset of one to five minutes, rather than a patch which will only start working after one hour, which would then be too late.
[5:45]Disease state. As mentioned previously, a tablet is not a suitable choice for a patient who is unconscious or vomiting.
[5:54]Lastly, the amount of drug required, which is usually based on a patient's choice, would they rather have 21 tablets per month or one patch per month. I hope this sums up the concept of pharmaceutics and dosage forms. Thanks for watching.
