By S. Sinikar. Mansfield University.

Atovaquone (Mepron) is used for both prophylaxis and Pyrantel (Antiminth) is effective in infestations of round- treatment of PCP in people who are unable to take TMP-SMX discount purinethol 50 mg otc. The drug acts locally to Adverse effects include nausea purinethol 50 mg low price, vomiting, diarrhea, fever, in- paralyze worms in the intestinal tract. Pyrantel is contraindicated in tion in HIV-seropositive patients who are unable to tolerate pregnancy and is not recommended for children younger than TMP-SMX. Common side effects include nausea/ hookworms, roundworms, and whipworms. In trichinosis, must be used with leucovorin rescue) approved only for treat- thiabendazole decreases symptoms and eosinophilia but does ment of moderate to severe PCP in immunocompromised pa- not eliminate larvae from muscle tissues. The mechanism of tients, including those with advanced HIV infection who are anthelmintic action is uncertain but probably involves inter- unable to take TMP-SMX. For other types of helminthiasis, it is usually consid- Dosage of trimetrexate must be reduced, and dosage of leu- ered an alternative drug. It is rapidly absorbed after oral covorin must be increased with significant neutropenia or administration and most of the drug is excreted in urine thrombocytopenia. It should be used with caution in clients with Pentamidine (Pentam 300, NebuPent) may be used both liver or kidney disease. Pentamidine Ivermectin (Stromectol) is used for numerous parasitic interferes with production of ribonucleic acid (RNA) and de- infections and is most active against strongyloidiasis. The drug is mectin has also been used for the oral treatment of resistant given parenterally for treatment of PCP and by inhalation for lice. It is excreted by the kidneys and accumulates in some nausea and vomiting. Clinicians should also be aware that the intravenous (IV) form of pentamidine is par- Scabicides and Pediculicides ticularly pancreotoxic.

Additional characteristics of the respiratory system and the the nasal mucosa purinethol 50mg mastercard. When the nasal passages are blocked generic 50mg purinethol free shipping, the process of respiration are described in the following sections. Respiration Pharynx, Larynx, and Trachea Respiration is the process of gas exchange by which O2 is ob- tained and CO2 is eliminated. This gas exchange occurs be- Air passes from the nasal cavities to the pharynx (throat). The pharynx con- specifically, the four parts of respiration are: tains the palatine tonsils, which are large masses of lymphatic • Ventilation—the movement of air between the atmos- tissue. It contains the and body cells vocal cords and forms the upper end of the trachea. It closes 694 CHAPTER 46 PHYSIOLOGY OF THE RESPIRATORY SYSTEM 695 on swallowing to prevent aspiration of food and fluids into rubber band) to expel air. It is a cartilaginous tube lined with cili- In addition to exchanging O2 and CO2, the lungs synthesize, ated epithelium and mucous-secreting cells. Cilia and mucus store, release, remove, metabolize, or inactivate a variety of help to protect and defend the lungs. These substances, which may be locally released or carried in blood or tissue fluids, partici- pate in both physiologic and pathologic processes. Specific sub- Lungs stances that may be released from the lungs include biogenic amines (eg, catecholamines, histamine, serotonin), arachi- The lungs begin where the trachea divides into the right and donic acid metabolites (eg, prostaglandins, leukotrienes), left mainstem bronchi and contain the remaining respiratory angiotensin-converting enzyme, and heparin. They are divided into five lobes, each with a sec- important in regulating smooth muscle tone (ie, constriction ondary bronchus. The lobes are further subdivided into bron- or dilation) in the airways and blood vessels. Heparin helps to dissolve blood clots, especially in the a venule, and a lymphatic vessel. The lungs also through a pulmonary artery and exits through a pulmonary process peptides, lipids, hormones, and drugs and inactivate vein.