Respiratory+&+Gastrointestinal+Drugs

Use this site to develop the concepts surrounding respiratory & gastrointestinal drugs and their mechanism of action.
**Gastrointestinal drugs

Describe them : Many drugs, both OTC and on prescription, are used for GI diseases. Some are used to treat specific GI diseases and others are used to provide symptomatic relief **
 * GERD- ** **“heartburn” the most prevalent GI disease in US. The stomach contents, including the acid, reflux, or flow backward through the cardiac sphincter, up into the esophagus, which then causes inflammation, irritation, and erosion. Can be treated by decreasing the acid in the stomach and to constrict the cardiac sphincter. H2-blockers and proton pump inhibitors (PPI’) reduce or eliminate the stomach acid. GI stimulants act by increasing the tone in the cardiac sphincter. Antacids are also used for acute relief of symptoms. **


 * Ulcers- ** **may occur in the stomach or the small intestines. Most ulcers are related in some way to the presence of the organism //Helicobacter pylori //. May can be cured by using a combination of one or more antibiotics and an h2 blocker or PPI to reduce the acid in the stomach. Some ulcers are caused chronic use of NSAIDS and to cure them you use Cytotec. 

Indication for use – Treatment of ulcers and the management of the symptoms of ulcers and GERD. Combining h2-blockers with antacids has no therapeutic advantage; actually antacids inhibit their absorption and should not be administered within 1 hour of h2-blockers. H2-blockers should be taken with meals and at bedtime, with the bedtime being the most effective if taken once a day. Smoking increases acid production and reduces the effect of the H2-blockers, therefore smoking cessation assistance should be offered to dental patients that smoke. Mechanism of action – Histamine2- blocking agents- Receptor antagonists that block and inhibit basal and nocturnal gastric acid secretion by competitive inhibition of the action of histamine at the h2-receptors of the parietal cells. Also inhibit gastric acid secretion stimulated by other agents such as food and caffeine. These drugs are available OTC and some examples include: Tagamet, Pepcid, Zantac, and Axid.  Possible adverse reactions- CNS- (Cimetidine), slurred speech, delusions, confusion, and headache Has antiandrogenic effects- reduction in sperm, sexual dysfunction (famotidine and ranitidine have not been found to have these effects)**Famotidine is associated with dry mouth and taste alterations All H2- receptors have been reported to have reversible hepatitis and abnormal liver function Cimetidine also inhibits liver microsomal enzymes responsible for the hepatic metabolism of some drugs causing a delay in elimination and an increase in serum levels of some drugs possibly producing toxicity. Ranitidine inhibits the P-450 enzymes much less than cimetidine, some drugs that are metabolized by the P-450 pathway include: Warfarin, lidocaine, diazepam, and theophylline.

Omerprazole (prilosec)- first PPI marketed and is a potent inhibitor of gastric acid secretion. Is effective (in combination with antibiotics) in healing both gastric and duodenal ulcers and approved to treat GERD. Mechanism of action includes the inhibition of H/K ATPase enzyme system at the surface of the gastric parietal cell and is called a gastric acid (proton) pump inhibitor. Side effects include; headache, and abdominal pain. Reported side effects include mucosal atrophy of the tongue and dry mouth. Another PPI is lansoprazole.
 * <span style="color: #ff00ff; font-family: Arial,Helvetica,sans-serif;">Protein pump inhibitors **

<span style="color: #ff00ff; font-family: Arial,Helvetica,sans-serif;">Used to treat a variety of gastric conditions such as acute gastritis and symptoms of ulcers. Acute gastritis is the common “heartburn” and upset stomach and symptoms include epigastric discomfort or a burning feeling. Antacids are drugs that partially neutralize hydrochloric acid in the stomach. These drugs achieve this by raising the pH to 3-4, therefore the erosive effect of the acid is decreased and pepsin activity is reduced. Antacids are classified as systemic or nonsystemic depending on the amount of absorption from the GI tract. Sodium bicarbonate is the only systemic antacid and rapidly neutralizes gastric acid. A disadvantage is the increase risk for alkalosis. Also due to the sodium it is contraindicated in cardiovascular patients who are to watch their sodium uptake. For these reasons it is not recommended.
 * <span style="color: #ff00ff; font-family: Arial,Helvetica,sans-serif;">Antacids **

Other GI drugs Misoprostol (Cyotec)- is used in the management of NSAID-iduced ulcers. Both H2-blockers and PPIs reduce the symptoms but do not prevent the ulcers. Misoprotsol increases gastric mucus and inhibits gastric acid secretion. Side effects include stomach distress and diarrhea. Contraindicated in pregnant patients. Sucralfate (Carafate)- is a complex of aluminum hydroxide and sulfated sucrose and is used to treat duodenal ulcers. In the stomach the aluminum ion splits off, leaving an anion that is essentially nonabsorbable. Sucralfate combines with proteins, forming a complex that binds preferentially with the ulcer site. Can be considered a “bandage” as it inhibits the action of pepsin and absorbs the bile salts. Its acid-neutralizing capacity does not contribute to its antiulcer action. Side effects include: constipation, dry mouth, nausea, rash, and dizziness. Must be taken on an empty stomach and can inhibit the absorption of tetracycline. Metoclopramine (Reglan)- is a dopaminergic antagonist that blocks the action of dopamine and that action facilitates cholinergic effects within the GI tract. Stimulates the motility of the upper GI tract without stimulating secretions and relaxes smooth muscle innervated by dopamine. It relaxes the pyloric sphincter and increase perstialsis in the duodeum. Result is an accelerated gastric emptying time and also increases the tone of the lower esophageal sphincter. Use for relief of symptoms associated with diabetic gastroparesis and improves delayed gastric emptying time. Also short term therapy for gastroesophageal reflux with symptoms. Side effects include CNS restlessness, drowsiness, and fatigue also Parkinson-like reactions can occur, nausea and diarrhea. Not to be used with other CNS depressants. Simethicone (Mylicon, Gas-X)- agent used to treat flatulence (gas) as it lowers the surface tension and breaks up gas pockets so they can be expelled.

Laxatives Laxatives- self-medicated laxatives are a common practice among the lay public. There are few indications for use, overuse is common and habituation can result. Abuse occurs in bulimic patients. Ligitimate include short-term occasional use for constipation and use before diagnostic procedures. There are four types of laxatives. Bulk laxatives- preferred because they are the safest and act most like the normal physiological of humans. They contain polysaccharides or cellulose derivatives that combine with intestinal fluids to form gels. This increases peristalsis and facilitates movement through the intestine. Lubricants- mineral oil, a lubricant that was previously often used, is no longer recommended. It can be absorbed if used over a long period and can interfere with the absorption of the fat-soluble vitamins (A, D, E, K) Stimulants- these laxatives act by producing local irritation of the intestinal mucosa. Intestinal cramping can result due to its potent effect. Bisacodyl, a member of this group is often used before bowel surgery or radiographic examinations but should not be used for simple constipation. Stool softeners (emollients)- Dicotyl sodium sulfossuccinate, an anionic detergent, wets and softens the stool by accumulating water in the intestines. These agents should be limited to short-term use, although they are termed nontoxic. Osmotic (saline) laxatives- Magnesium sulfate or phosphate produces its laxative effect by osmotically holding water. It should be used with caution in patients with renal impairment.


 * **Categories of Diuretics** || **Indication of Use** ||
 * K+ Sparing Diuretics || Most often used to prevent hypokalemia, but is also used for the treatment of hyperaldosteronism, and congestive heart failure. ||
 * Thiazide Diuretics || Is primarily used for the treatment of hypertension, they can also mobilize mild edema and reduce the concentration of Ca+ in excreted urine which can prevent the formation of renal stones. ||
 * Loop Diuretics || Are primarily used for the treatment of edema and is the drug of choice for volume management in renal failure. ||
 * Osmotic Diuretics || They increase or maintain urine flow to prevent the progression renal failure and helps remove toxins from the body. It can also be used to decrease brain edema and intracranial pressure, and for preoperative treatment to lower intraocular pressure before surgery for glaucoma ||

Antidiarrheals Drugs used to treat diarrhea are either absorbents or opioid-like in action. Antidiarrheals are used to minimize fluid and electrolyte imbalances. In certain poisoning or infections, antidiarrheals are used to minimize fluid and electrolyte imbalances. In certain poisoning or infections, antidiarrheals are contraindicated. Most common absorbent combination used to treat diarrhea is kaolin and pectin (Kaopectate). The opioids such as diphenoxylate with atropine (Lomotil) and loperamide (OTC Imodium), are the most effective antidiarrheal agents. They decrease peristalsis by acting directly on the smooth muscle of the GI tract.

Emetics Ipecac is an emetic used to treat persons who hae ingested an overdose of drugs that could be harmful. It has been abused by individuals with bulimia. Over time, with chronic use, the body becomes resistant to the emetic effect and the ipecac is absorbed. The cardiac toxicity produced by the retained ipecac has been fatal to patients with bulimia.

=Respiratory Drugs=

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 12pt; line-height: 27px;">Drugs used to treat:


 * **<span style="font-family: Arial,Helvetica,sans-serif;">Asthma **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">Chronic obstructive pulmonary disease (COPD) **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">Upper respiratory infections **


 * <span style="font-family: Arial,Helvetica,sans-serif;">Asthma **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Is reversible airway obstruction and is associated with reduction in expiratory airflow.
 * <span style="font-family: Arial,Helvetica,sans-serif;">A few hours later inflammation occurs resulting in an increase in secretions in the lungs and swelling in the bronchioles.
 * <span style="font-family: Arial,Helvetica,sans-serif;">When asthma is treated both parts must be treated.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Asthma may be precipitated by allergens, pollution, exercise, stress, or upper respiratory infections.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Aspirin should be avoided in patients with asthma and erythromycin may alter the metabolism of therophylline.


 * <span style="font-family: Arial,Helvetica,sans-serif;">COPD **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Is characterized by irreversible airway obstruction, which occurs with either chronic bronchitis or emphysema.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Smoking is associated with almost all COPD.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Chronic bronchitis is a result of chronic inflammation of the airways and excessive sputum production.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Emphysema is characterized by alveolar destruction with airspace enlargement and airway collapse.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Patient's with severe COPD can develop pulmonary hypertension, increasing risk for cardiac arrhythmias

=Drugs Used to Treat Asthma=

Bronchodilators

 * **B2-selective Adrenergic Drugs**
 * ** Ex.: Albuterol **
 * The most commonly prescribed B2-adrenergic bronchodilator
 * Administered by:
 * Tablet form
 * Metered-dose inhaler
 * To be used if an asthmatic attack occurs in the dental office
 * **Other Adrenergic Agonists**
 * ** Ex.: Epinephrine **
 * Adminstered by:
 * Oral inhalation by a nebulizer
 * Metered-dose inhaler
 * Subcutaneous injection - reserved for acute episodes of asthma requireing immediate relief when inhaled B2-selective agonists have proved ineffective or could not be effectively administered.

Antiinflammatory Drugs

 * **Corticosteroids**
 * Topical steroid aerosols
 * ** Ex.: Fluticasone **
 * Effective and safe for long-term treatment of asthma
 * Oral corticosteroids
 * Parental corticosteriods
 * **Nonsteroidal prophylactic drugs**