[0:01]So in our consideration of giving drugs, we've talked about systemic effects, dividing those into enteral and parenteral. We now want to think about local administration of medications. So the systemic is going around the whole body, going everywhere. Local is only affecting one part of the body. So how might we give drugs for local administration? Well, a fairly obvious one is uh, eyes. Giving medication into eye, so we can give eye drops or we can give eye ointments. So for example, we might give an antibiotic ointment if there was a conjunctivitis. Or we might give drops to dilate the pupil to facilitate an examination or we might give drops of local anaesthetic if we wanted to remove a foreign body from the eye or fluorescein if we wanted to identify corneal abrasions. So eye drops will give quite commonly. Another possible local administration is nasal. Giving medications into the nose. So for example, there might be adrenaline-based administrations to deal with nosebleeds, epistaxis. The adrenaline preparations can bring about some localized vasoconstriction to reduce the bleed. So sometimes we give drugs into into the nose. And I think what I'll do now is mention an important principle when we give drugs locally, that while we give nasal preparations very often for a local effect, because the nasal cavities are very vascular, there can also be some systemic absorption. So this could almost be a side effect. Now, sometimes drugs might be given nasally with the express purpose of having systemic absorption, you might think of people abusing cocaine, for example. Where the whole point is to get the drug to the brain, but just bear in mind, there's local effects, but many drugs can be systemically absorbed as well. And we'll see this repeatedly when we're thinking about giving drugs for local application. Another one is inhalation. Inhaling drugs, so you might think for example of nebulizers. We might nebulize salbutamol or ipratropium. The idea here is that the nebulized drug goes down into the bronchioles, the small bronchial passages and facilitates bronchodilation. Or we might give steroid inhalers to reduce inflammation and give them via nebulizers or sometimes we give them via puffers where we inhale via puffers. And again, bear in mind that yes, these are going to work locally, but they can also have systemic effects. So for example, if you've given nebulized salbutamol, then the patient's on a cardiac monitor. We'll normally notice an increase in heart rate, there'll be a degree of tachycardia because the salbutamol is a sympathetic stimulant, that is how it is dilating the bronchial passages. Some of that will act locally and bring about bronchodilation, which is the desired effect, but there can also be some systemic absorption of the salbutamol, stimulating the sympathetic receptors, increasing heart rate. Ears is another one. We sometimes give preparations into ears, thinking about into the outer ear canal, the external auditory meatus. Very often things to dissolve wax, such as olive oil for dissolving wax or other preparations. Now, topical, topical just means onto the surface of the skin, so any any preparation that we put onto the surface of the skin, ointments and things like that, that's a topical administration, we're putting it onto the surface of the body. Sometimes we can give injections into joints. So perhaps steroid injections for rheumatoid arthritis or other unwanted inflammatory conditions of joints, vital of course not to do that if there's any infection because the anti-inflammatory effect would not be desirable if there's infection, but if there's idiopathic anxiety, such as uh auto-immune diseases such as rheumatoid arthritis, it can be highly desirable. We can give drugs directly into the peritoneum. The peritoneal cavity or the peritoneal, yeah, the peritoneal cavity is the potential space between the visceral and parietal peritoneal membrane in the abdomen. And we might take advantage of this potential space, turning it into an actual space, for example, if we were doing peritoneal dialysis and sometimes we could add drugs to the dialysate. This can have a local effect such as antibiotics, but of course, the peritoneum is a very large well, it contains lots and lots of small blood vessels and capillaries, so the potential for systemic absorption is significant. Now, you can call these, I call them pessaries, or you can call them vaginal suppositories. So pessaries or vaginal suppositories are preparations we would insert directly high into the vagina, such as anti-fungal preparations if there was a monilial infection, for example. Another possibility is rectal. Now, we did talk about PR drugs when we were talking about systemic absorption, but other things we give specifically for their local effect. So for example, we might give an enema or suppositories, we might give a suppository to stimulate bowel activity and facilitate defecation if there's constipation. And occasionally we might put drugs into the bladder if there's a catheter in situ, perhaps antibiotic or antibacterial preparations or cytotoxic preparations if there was malignancy, not done commonly, but we do do it sometimes.
[7:31]Now, I think I'll do anesthesia as a separate thing, anesthesia to reduce pain. And this can be regional or it can be local. Now what we mean here is a regional anesthetic, for example, if we anaesthetize the femoral nerve going into the leg, because this supplies a lot of the leg that could anaesthetize large parts of the leg. So for example, if someone's got a fracture of the femur, we might give a femoral nerve block to take away the pain from that part of the body, that would be a regional, the region of the body would be anaesthetized in in this area. Or sometimes we might give epidurals or intrathecal preparations into the spinal cord, and that would anaesthetize the bottom half of the body, which is often highly desirable as well. Or other times we just want to suture up a cut, so we'll just give a little bit of local anaesthesia into the area so we can close up a small wound. So regional can be nerve blocks, could be epidural, into the epidural space, intrathecal, would be directly into the cerebrospinal fluid.
[9:04]Whereas local is just going to block local nociceptors. Or the dendrites leaving local nociceptors. So there we have quite a few ways that if you're in any form of health care, you will be involved in giving drugs via these methods via these routes. These are all local. So remember that is an extension of uh that was our original one. That's all an extension of that, of course. And this mind map, so uh, we've looked at systemic versus local, but we've also noted, and this is very important, that when we give drugs locally, there is the potential for systemic absorption and systemic effects, and we do need to take account of that, because these systemic effects may be wanted, but then again, they may be unwanted systemic effects as well. So don't give too much local lignocaine, because that will be absorbed and it will have adverse effects on the myocardium, for example. So always bear in mind the possibility that local drug administration can give rise to some systemic absorption and therefore systemic effects.
