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Оглавление1 Drugs that affect the gastrointestinal system
Aminosalicylates
Antimuscarinics
Antispasmodics
Direct‐acting smooth muscle relaxants
H2‐receptor antagonists
Laxatives
Proton pump inhibitors (PPIs)
Note: antimuscarinics are drugs that can also be used to treat respiratory disorders (see Chapter 4), bradycardia, genitourinary disorders and Parkinson's disease (see Chapter 5) and nausea and vomiting (see Chapter 7).
Aminosalicylates
Aminosalicylates are anti‐inflammatory drugs given to treat gastric inflammation associated with conditions such as ulcerative colitis and Crohn's disease. Aminosalicylates are derivatives of salicylic acid: a natural substance originally obtained from willow bark, which has been used as a medicine for thousands of years (Hippocrates had written about the therapeutic properties of willow as far back as 400 B.C.). The Latin term for willow is ‘salix’, from which is derived the word ‘salicylic’. The active ingredient in willow – salicin – metabolises in the body into salicylic acid. In the nineteenth century salicylic acid began to be produced synthetically. In addition to aminosalicylates, salicylic acid is now the basic ingredient in a number of related anti‐inflammatory drugs, including aspirin (acetylsalicylic acid: see Chapters 3 and 6). Aminosalicylates have generic names that contain the letters ‘‐sal‐’, resulting in names ending in either ‘‐salazide’ or ‘‐salazine’:
Balsalazide
Mesalazine
Olsalazine
Sulfasalazine
Despite sharing the same ‘sulfa‐’ prefix, do not mistake the aminosalicylate sulfasalazine for one of the sulfonamide class antibiotics (i.e., sulfamethoxazole: see Chapter 9).
Do not mistake the antihypertensive drug hydralazine for an aminosalicylate with a name ending in ‘‐salazine’. Hydralazine is a direct‐acting vasodilator of a type known as a ‘hydrazinophthalazine’.
Antispasmodics
Antispasmodics are drugs used to bring symptomatic relief from gastrointestinal muscle spasm in patients with conditions such as irritable bowel syndrome (IBS) (Ruepert et al., 2011). The term ‘antispasmodic’ simply describes what these drugs do (relaxing intestinal smooth muscle) and does not refer to just one type or class of drug. Medicines that have antispasmodic (or ‘spasmolytic’) properties include antimuscarinics and direct‐acting smooth muscle relaxants.
Antimuscarinic antispasmodics
Antimuscarinics work by reducing intestinal motility (see list of other antimuscarinic drugs in Chapter 5).
Atropine
Dicycloverine
Hyoscine butylbromide
Propantheline
Direct‐acting smooth muscle relaxants
Direct‐acting smooth muscle relaxants are medicines used to help relieve the symptoms of abdominal colic and IBS (Ford et al., 2008).
Alverine
Mebeverine
Peppermint oil
The suffix ‘‐verine’ is one that can be applied to any drug with smooth muscle relaxing properties (i.e., the antimuscarinic propiverine (used to relax smooth muscle in the bladder: see Chapter 5) and the phosphodiesterase inhibitor papaverine (see Chapter 8).
H2‐receptor antagonists
An amino acid called histidine is a precursor to histamine; with histamine‐2 playing an important role in helping stimulate gastric acid secretion. H2‐receptor antagonists (the ‘H’ stands for histamine) are a particular type of antihistamine that works by selectively blocking histamine‐2 receptors (also see H1 receptor‐blocking ‘antihistamines’: see Chapter 5).
H2‐receptor antagonists reduce gastric acid secretions and so help protect the stomach's mucosal lining from acid erosion (Keshav and Bailey, 2013, pp. 43, 73–75). Cimetidine – the first H2‐receptor antagonist – was introduced in 1976 and soon became the first prescription drug in the world to achieve annual sales worth more than one billion dollars, ushering in (for better or worse) the era of ‘blockbuster’ selling drugs.
H2‐receptor antagonists are prescribed to treat gastrointestinal disorders such as gastric or duodenal ulcers, oesophageal reflux and dyspepsia (Puttmann and Roett, 2011). H2‐receptor antagonists (often referred to as ‘H2 blockers’) can be recognised by generic drug names ending with the letters ‘‐tidine’:
Cimetidine
Famotidine
Nizatidine
Ranitidine
Note a few exceptions: drugs with names ending in ‘‐tidine’ but which are not H2‐receptor antagonists: azacitidine (a chemotherapy drug: see Chapter 10) and hexetidine (an antiseptic mouth wash).
Laxatives
Laxatives (also known as aperients or purgatives) are given to treat or prevent constipation. There are various types: bulk‐forming laxatives (i.e., ispaghula husk and sterculia) that act by increasing faecal mass; osmotic laxatives (i.e., lactulose) that draw water into the bowel; faecal softeners (i.e., docusate sodium and poloxamer ‘188’) that ease rectal straining and stimulant laxatives (i.e., bisacodyl, dantron, senna and sodium picosulfate) that promote peristalsis and bowel motility. Co‐danthramer (which combines dantron with poloxamer ‘188’) and co‐danthrusate (which combines dantron with docusate sodium) are both compound laxatives (hence their ‘co‐’ prefix). Prucalopride is a selective 5HT‐4 receptor agonist: it promotes bowel motility by enhancing the transmission of serotonin‐4 (5HT‐4) to 5HT‐4 receptors in the colon.
Bisacodyl
Co‐danthramer
Co‐danthrusate
Docusate sodium
Ispaghula husk
Lactulose
Prucalopride
Senna
Sodium picosulfate
Sterculia
Do not confuse dantron (a component of both co‐danthramer and co‐danthrusate) with the antiemetic ondansetron (see Chapter 7). Similarly, do not mistake the laxative prucalopride for a benzamide class antipsychotic (i.e., amisulpride, see Chapter 5).
Proton pump inhibitors (PPIs)
The parietal cells in the stomach release a stream of enzymes known as the hydrogen–potassium adenosine triphosphatase enzyme system (commonly called ‘the proton pump’). This is the final (and crucial) step in the process of gastric acid secretion. Proton pump inhibitors (PPIs), as their name indicates, are drugs that inhibit the proton pump, thereby reducing gastric acid secretion. PPIs are effective in treating dyspepsia, oesophageal reflux, in preventing or treating peptic ulcers and in helping eradicate Helicobacter pylori (Strand et al., 2017). First introduced in the late 1980s, PPIs are now among the most commonly prescribed drugs in the world (Savarino et al., 2017). PPI names end in ‘‐prazole’.
Esomeprazole
Lansoprazole
Omeprazole
Pantoprazole
Rabeprazole
Note an exception: a drug ending in ‘‐prazole’ that is not a proton pump inhibitor: aripiprazole (an atypical antipsychotic drug: see Chapter 5).
Do not mistake PPIs ending in ‘‐prazole’ for antibiotics ending in ‘‐nidazole’ (i.e., metronidazole) or ‘‐oxazole’ (i.e., co‐trimoxazole) (see Chapter 9); or antifungals ending in ‘‐conazole’ (i.e., fluconazole: Chapter 9) or hormone antagonists ending in ‘‐rozole’ (i.e., letrozole: Chapter 10) [chemically, all of the above are azole derivatives, hence their ‘‐zole’ suffix].
References
1 Ford, A.C., Talley, N.J., Spiegel, B.M. et al. (2008). Effect of fibre, antispasmodics and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta‐analysis. British Medical Journal, 337, a2313.
2 Keshav, S. and Bailey, A. (2013). The gastrointestinal system at a glance. 2nd ed. Chichester: Wiley Blackwell.
3 Puttmann, M. and Roett, M.A. (2011). H2 blockers are as effective as PPIs for long‐term relief of non‐ulcer dyspepsia. Evidence‐Based Practice, 14 (2), 14.
4 Ruepert, L., Quartero, A.O., de Wit, N.J. et al. (2011). Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database of Systematic Reviews [online]. Available from: doi: 10.1002/14651858.CD003460.pub3.
5 Savarino, V., Dulbecco, P., de Bortoli, N. et al. (2017). Appropriate use of proton pump inhibitors (PPIs): need for a reappraisal. European Journal of Internal Medicine, 37, 19–24 [online]. Available from: doi: 10.1016/j.ejim.2016.10.007.
6 Strand, D.S., Kim, D. and Peura, D.A. (2017). 25 years of proton pump inhibitors: a comprehensive review. Gut and Liver, 11 (1), 27–37 [online]. Available from: doi: 10.5009/gnl.15502.
