Lansoprazole

Question 1

What is the drug usually used for?

Answer 1

Acid reflux

Peptic ulcer disease

Elimination of H.pylori

Severe oesophagitis

Zollinger-Ellison syndrome

Question 2

Describe the pharmacodynamics of this drug

Answer 2

A proton pump inhibitor

Decreases gastric acid secretion by targeting the H+/K+-ATPase - an enzyme that catalyses the final step of the acid secetion pathway in parietal cells.

Also reduces pepsin secretion

Question 3

What is the Zollinger-Ellison syndrome?

Answer 3

A rare condition caused by the formation of one or more tumours (gastrinomas) in the pancreas or the duodenum.

Gastrinomas secrete large amounts of gastrin.

This over stimulates the stomach causing excess acid production.

Question 4

Describe the pharmacokinetics of this drug

Answer 4

Oral bioavailability = 80-90% (Cmax achieved 1.7 hours after oral dosing)

Protein binding = 97%

Volume of distribution = 0.4L/kg

Half-life = 0.9 - 2.1 hours

Metabolism = liver (via CYP3A4 & CYP2C19)

Excretion = kidneys (14-23% of lansoprazole). Clearance is 400-650 mL/min.

Question 5

What are the contraindications of this drug?

Answer 5

Avoid during pregnancy or breastfeeding

Question 6

What are most clinically significant (common and/or potentially life threatening) side effects of the drug?

Answer 6

The common/very common side effects are:

• dry throat
• fatigue

The uncommon side effects are:

• eosinophillia
• oedema

The rare/very rare side effects are:

• oesophageal candidiasis
• pancreatitis
• angioedema

Question 7

Is any monitoring required?

Answer 7

Consider measuring serum Mg2+ before prolonged treament with PPIs (especially when used with other drugs that cause hypomagnesaemia or with digoxin)

Question 8

When should the dose of Lansoprazole be reduced and by what %?

Answer 8

In moderate to severe hepatic impairment

By 50%

Question 9

What are the most clinically significant drug interactions?

Answer 9

May interfere with the absorption of other drugs where gastric pH is an important determinant of oral bioavailability (e.g. HIV proteases, ketoconazole and itraconazole).

It may increase plasma concentrations of medicinal products that are metabolised by CYP3A4

Warfarin + Lansoprazole = increased INR & PT which can lead to abnormal bleeding and even death

Question 10

What are the general side effects of PPIs?

Answer 10

The common/very common side effects are:

• abdominal pain
• headache
• dry mouth
• vomiting
• headache

The uncommon side effects are:

• athralgia/myalgia
• confusion
• depression
• thrombocytopenia

The “frequency unknown” side effects are:

• agranulocytosis
• pancytopenia
• hepatic disorders