Student Formulary

Question 1

Aminosalicylates examples

Answer 1

Sulfasalazine (now more commonly used as a DMARD in Rheumatoid Arthritis)

Mesalazine

Question 2

Aminosalicylates indications

Answer 2

Crohn’s disease or Ulcerative colitis. These drugs are used in mild - moderate inflammatory bowel disease to treat acute exacerbations and to reduce remission rates.

Question 3

Aminosalicylates contraindications

Answer 3

Salicylate hypersensitivity
Sulfasalazine – avoid in children under 2 years old

Question 4

CAUTION Aminosalicylates

Answer 4

Renal Impairment
Pregnancy
Breast Feeding
G6PD Deficiency

Question 5

mechanism aminosalicylates

Answer 5

The mechanism of action is unknown, however there are several possible anti-inflammatory actions which may be important at the affected site. Aminosalicylates act as free radical scavengers, inhibit prostaglandin and leukotriene production, and reduce release of IL-1 from cells.

Question 6

aminosalicylates administration

Answer 6

Oral

PR (enema or suppository)

Mesalazine should be prescribed by brand rather than generically as there can be some characteristic differences between brands.

Question 7

common adverse reactions Aminosalicylates

Answer 7

GI disturbance

Question 8

rare adverse reactions Aminosalicylates

Answer 8

Blood dyscrasias
Renal dysfunction
Lupus like syndrome

Question 9

Aminosalicylates drug interactions

Answer 9

Increased risk of leukopenia if given with immunosuppressants such as azathioprine/mercaptopurine.

Proton pump inhibitors and lactulose have been found to reduce the release of mesalazine as these lower the gastrointestinal pH.

Sulfasalazine decreases the absorption of digoxin and folic acid.

Sulfasalazine can stain some soft contact lenses.

Question 10

education for patient on aminosalicylates

Answer 10

Regular monitoring of renal function is needed. Tell patient to report any unexplained bruising, rashes or infective symptoms as these could indicate a blood abnormality.

Question 11

pharmacokinetics aminosalicylate

Answer 11

The active molecule in these drugs is 5-aminosalicylate.

In sulfasalazine, 5-aminosalicylate is attached to a sulphonamide group. When this reaches the gut, bacteria cleave it into 5-aminosalicylate and sulphapyridine. It is the systemic absorption of sulphapyridine that causes side effects (like those seen with sulphonamide antibiotics).

Mesalazine is a 5-aminosalicylate in a form that will release that active ingredient in the gut. It has fewer side-effects than sulfasalazine due to the lack of a sulphonamide metabolite.

Question 12

Antimuscarinics examples

Answer 12

Hyoscine butylbromide (Buscopan)

Mebeverine

Dicycloverine

Question 13

indications for antimuscarinics

Answer 13

Symptomatic relief of gastrointestinal disorders characterised by smooth muscle spasm; bowel colic (e.g. Irritable bowel syndrome)

Question 14

contraindications of antimuscarinics

Answer 14

Contraindications
Paralytic ileus
Pyloric stenosis

Caution
Patients susceptible to acute angle closure glaucoma; an adverse effect of muscarinic antagonists is a rise in intraocular pressure, this may precipitate acute angle closure glaucoma.
Patients with bladder outflow obstruction and prostatic hyperplasia; an adverse effect of muscarinic receptor antagonists is relaxation of the bladder which causes urinary retention. In a patient with any degree of bladder outflow obstruction there is a risk of developing acute urinary retention.
Patients with myasthenia gravis; administration of muscarinic receptor anagonists may cause deterioration in symptoms.
Patients with underlying heart disease, particularly arrhythmias, as these can be worsened.

Question 15

mechanism of action of antimuscarinics

Answer 15

Parasympathetic stimulation causes the release of acetylcholine from the post ganglionic parasympathetic nerve endings, which then acts on cholinergic (muscarinic) receptors, specifically M3 receptors, causing parasympathetic effects.

Muscarinic antagonists inhibit smooth muscle constriction in the gut wall, producing muscle relaxation and reduction spasm.

Question 16

administration of antimuscarinics

Answer 16

In gastrointestinal conditions, muscarinic antagonists are administered orally.

Hyoscine is also available to give parenterally.

Question 17

adverse reactions of antimuscarinics

Answer 17

Muscarinic receptor antagonists are highly polar molecules and are usually administered by aerosol inhalation. As a result they are not well absorbed into the systemic circulation and hence have little action at muscarinic repceptors other than those found in the bronchi. This results in few unwanted effects.

Antagonism of the parasympathetic pathway at muscarinic receptors may lead to adverse effects on other glandular and smooth muscle (note antagonists are not selective and will block all three types of muscarinic receptor - M1, M2 and M3). If the parasympathetic pathway in these tissues is blocked this will result in unopposed sympathetic activity on the tissues, causing classic anti-cholinergic side effects:

Dilated pupils
Blurred vision
Dry mouth
Nausea
Constipation
Headache
Urinary retention / difficulty micturating
Tachycardia
Hypotension
Drowsiness/Confusion

Question 18

drug interactions of antimuscarinics

Answer 18

Care must be taken if prescribing other anti-cholinergic drugs. This may potentiate the effects of the muscarinic antagonists.