Bronchodilators

00:01 So, let's talk about bronchodilators. Now bronchodilator action is limited to taking that constricted inflammed airway and opening it up. The drug binds to the beta 2 receptor in the lung and it stimulates cyclic AMP in smooth muscle cells.

00:17 Those smooth muscles relax in the bronchial muscle and you get dilatation.

00:23 Now, obviously you're not fully treated because those airways are still kind of thick, aren't they? Short acting beta agonists generally last less than 6 hours such as albuterol.

00:35 Long acting beta agonists or LABAs act over 24 to 48 hours sometimes 12 hours. These are salmeterol, formoterol and so on.

00:45 Those drugs are used once or twice a day. Now, there is a drug specifically indicated for COPD that is also in the beta agonist list but we are going to leave that alone for now.

00:58 Toxicity of bronchodilators is pretty rare. You can sometimes get tachycardia or tremor and sometimes you can get hyperexcitibility, but as I said, because these are inflammed agents, you're not really going to have a lot of symptoms.

01:13 Methylxanthines are purine derivatives. Now caffeine is a methylxanthine.

01:18 So, when you think about effects and side effects, think about caffeine on your own body.

01:23 Theophylline is the prototypical respiratory methylxanthine. These drugs act by inhibiting phosphodiesterase.

01:32 And PDE3 activates bronchodilation. When you have these drugs on board, you may also increase diaphragmatic strength.

01:44 Two cups of coffee can actually cause bronchodilation so you can understand that these drugs may be quite potent.

01:52 The side effects are the same as drinking too much coffee. Gastrointestinal distress usually manisfested by cramping.

01:58 Tremor and insomnia. A toxicity of these agents can be arrhythmia and high blood pressure. And vomiting is also a potential side effect.

02:08 The antidote for these medications is beta blockers because you want to block the effects of hyperadrenergic states.

02:16 The next class of drugs are the muscarinic agents. The prototypical drug is ipatropium which is sold commonly as Atrovent.

02:25 When you look at the colour of puffer, its universal colour is going to be green or a green cap.

02:30 This agent will block muscarinic receptors in the airways. This prevent bronchoconstriction caused by vagal discharge.

02:39 So they may not be particularly effective if they have already constricted.

02:44 They may be used both in children and in adults. And these agents have no anti-inflammatory action.

02:52 The toxicity is minor atropine like effects so the toxicities are almost non existence.

02:58 They do not cause tremor and they do not cause arrhythmia which distinguishes these drugs from the beta agonists.