GP Gastroenterology PHARMACOLOGY

Mesalazine

drug class: Aminosalicylate (5-ASA). uses: Induction and maintenance of remission in mild-to-moderate ulcerative colitis. side effects: Nausea, diarrhoea, abdominal pain, headache and rash. important cautions: Monitor renal function as indicated; rare interstitial nephritis and blood disorders can occur. Report unexplained bruising, fever or reduced urine output.

Sulfasalazine

drug class: Aminosalicylate; conventional disease-modifying antirheumatic drug (DMARD). uses: Ulcerative colitis and inflammatory arthritis, including rheumatoid arthritis. side effects: Nausea, headache, rash, folate deficiency, reversible oligospermia and blood disorders. important cautions: Monitor full blood count, liver function and renal function. Avoid with relevant sulfonamide or salicylate hypersensitivity. Folate supplementation may be required.

Amitriptyline

drug class: Tricyclic antidepressant (TCA). uses: Depression; low-dose treatment of selected neuropathic pain and chronic pain conditions. side effects: Sedation, dry mouth, constipation, blurred vision, urinary retention and postural hypotension. important cautions: Potentially fatal cardiac toxicity in overdose. Review cardiac disease, glaucoma and urinary retention risk. Use caution in older adults.

Citalopram

drug class: Selective serotonin reuptake inhibitor (SSRI). uses: Depression; selected other indications according to guidance. side effects: Nausea, diarrhoea, sleep disturbance, sexual dysfunction and discontinuation symptoms. important cautions: Dose-related QT prolongation; consider cardiac risk and interacting medicines. Risk of serotonin syndrome with serotonergic combinations. Monitor for worsening mood and suicidal thoughts.

Sertraline

drug class: SSRI. uses: Depression, obsessive-compulsive disorder, panic disorder and other indicated anxiety disorders. side effects: Nausea, diarrhoea, sleep disturbance, sexual dysfunction and discontinuation symptoms. important cautions: Risk of serotonin syndrome and bleeding, particularly with NSAIDs or anticoagulants. Monitor mood and suicidal thoughts, especially early in treatment.

Fluoxetine

drug class: SSRI. uses: Depression, obsessive-compulsive disorder and selected other psychiatric disorders. side effects: Nausea, insomnia, agitation, sexual dysfunction and gastrointestinal upset. important cautions: Long half-life means interactions can persist after stopping. Risk of serotonin syndrome. Review interactions and monitor mood and suicidal thoughts.

Domperidone

drug class: Peripheral dopamine D2-receptor antagonist; antiemetic. uses: Short-term relief of nausea and vomiting when appropriate. side effects: Dry mouth, headache and raised prolactin; cardiac arrhythmias may occur. important cautions: Risk of QT prolongation, ventricular arrhythmia and sudden cardiac death. UK use is restricted: use the lowest effective dose for the shortest possible time, generally no longer than one week. Avoid in significant cardiac disease and with certain QT-prolonging medicines or potent CYP3A4 inhibitors.

Metoclopramide

drug class: Dopamine D2-receptor antagonist; prokinetic antiemetic. uses: Short-term treatment of nausea and vomiting in selected situations. side effects: Drowsiness, diarrhoea, restlessness and extrapyramidal symptoms. important cautions: Risk of acute dystonia and tardive dyskinesia. UK use is generally restricted to a maximum of five days. Avoid in gastrointestinal obstruction or perforation, Parkinson's disease and relevant seizure disorders.

Prochlorperazine

drug class: Phenothiazine; dopamine D2-receptor antagonist and antiemetic. uses: Nausea, vomiting and vertigo; also certain psychiatric indications. side effects: Drowsiness, postural hypotension, dry mouth and extrapyramidal symptoms. important cautions: May cause dystonia, QT prolongation and neuroleptic malignant syndrome. Use caution in older adults and with other sedating or QT-prolonging medicines.

Cinnarizine

drug class: H1 antihistamine with calcium-channel-blocking properties. uses: Motion sickness and vestibular symptoms, including vertigo. side effects: Drowsiness, nausea, weight gain and dry mouth. important cautions: May impair driving. Use caution in older adults and Parkinson's disease because movement symptoms may worsen.

Cyclizine

drug class: H1 antihistamine with antimuscarinic properties; antiemetic. uses: Nausea and vomiting, including motion sickness and selected postoperative or medication-related nausea. side effects: Drowsiness, dry mouth, blurred vision and constipation. important cautions: Anticholinergic effects can worsen urinary retention and angle-closure glaucoma. Avoid alcohol and take care with other sedatives.

Promethazine

drug class: First-generation H1 antihistamine; phenothiazine derivative. uses: Nausea, vomiting, motion sickness and allergy-related symptoms; sometimes used for short-term sedation. side effects: Marked drowsiness, dry mouth, blurred vision, constipation and postural hypotension. important cautions: Avoid alcohol and other sedatives where possible. Anticholinergic effects may worsen glaucoma or urinary retention. Use particular caution in children and follow age-specific product restrictions.

Ondansetron

drug class: Serotonin 5-HT3-receptor antagonist; antiemetic. uses: Prevention and treatment of nausea and vomiting, including chemotherapy-related or postoperative symptoms. side effects: Constipation, headache and flushing. important cautions: QT prolongation and arrhythmia risk, especially with electrolyte abnormalities or other QT-prolonging medicines. Can worsen constipation; seek assessment if severe abdominal distension suggests ileus.

Hyoscine butylbromide

drug class: Antimuscarinic antispasmodic. uses: Relief of gastrointestinal smooth-muscle spasm and abdominal cramps. side effects: Dry mouth, tachycardia, blurred vision and constipation. important cautions: Avoid in myasthenia gravis, megacolon and mechanical gastrointestinal obstruction; use caution in glaucoma and urinary retention. Severe or persistent abdominal pain needs assessment rather than repeated symptom suppression.

Glycopyrronium

drug class: Antimuscarinic; the formulation determines the indication. uses: Oral or injectable forms may reduce secretions; inhaled forms are long-acting bronchodilators for COPD. side effects: Dry mouth, constipation, urinary retention and blurred vision. important cautions: Check the formulation before use because inhaled and systemic products are not interchangeable. Use caution with glaucoma, urinary retention and other anticholinergic medicines.

Azathioprine

drug class: Thiopurine immunosuppressant; purine analogue. uses: Inflammatory bowel disease maintenance in selected patients, autoimmune disease and prevention of transplant rejection. side effects: Bone-marrow suppression, nausea, liver toxicity, infections and pancreatitis. important cautions: Monitor full blood count, liver function and renal function. TPMT/NUDT15 status may inform prescribing. Allopurinol and febuxostat can cause dangerous increases in exposure; specialist dose adjustment or avoidance is essential.

Mercaptopurine

drug class: Thiopurine antimetabolite immunosuppressant. uses: Selected inflammatory bowel diseases and haematological malignancies under specialist care. side effects: Bone-marrow suppression, liver toxicity, nausea, infections and pancreatitis. important cautions: Requires blood-count and liver monitoring. TPMT/NUDT15 status is relevant. Allopurinol and febuxostat have major interactions and require specialist management.

Methotrexate

drug class: Antimetabolite; conventional DMARD and immunosuppressant. uses: Inflammatory bowel disease in selected specialist-managed cases; rheumatoid and psoriatic arthritis and other inflammatory conditions. side effects: Nausea, mouth ulcers, liver toxicity, bone-marrow suppression and pneumonitis. important cautions: For inflammatory disease, it is usually taken ONCE WEEKLY, not daily. Overdose can be fatal. Monitor full blood count, liver and renal function. Avoid in pregnancy when contraindicated; review interactions, infection risk and alcohol intake.

Macrogol 3350

drug class: Osmotic laxative (polyethylene glycol). uses: Constipation; some preparations are used for faecal impaction. side effects: Bloating, abdominal pain, nausea and diarrhoea. important cautions: Maintain adequate fluid intake. Avoid when bowel obstruction or perforation is suspected. Follow preparation-specific instructions; electrolyte-containing products may need extra consideration in vulnerable patients.

Lactulose

drug class: Osmotic laxative. uses: Constipation; also used to reduce ammonia in hepatic encephalopathy. side effects: Flatulence, abdominal cramps and diarrhoea. important cautions: Excessive doses can cause dehydration and electrolyte disturbances. For hepatic encephalopathy, dosing and monitoring should follow specialist advice.

Senna

drug class: Stimulant laxative. uses: Short-term relief of constipation; sometimes used with opioids to prevent constipation. side effects: Abdominal cramps, diarrhoea and electrolyte disturbances with excessive or prolonged use. important cautions: Avoid if intestinal obstruction is suspected. Persistent use can cause fluid and electrolyte imbalance; investigate ongoing constipation rather than relying on regular unsupervised use.

Docusate sodium

drug class: Stool softener (emollient laxative). uses: Constipation when softening stool is desirable. side effects: Abdominal cramps, diarrhoea and nausea. important cautions: Avoid in suspected bowel obstruction. Check interactions and product-specific restrictions, particularly if taking mineral oil.

Glycerol

drug class: Rectal osmotic laxative; suppository. uses: Short-term relief of constipation. side effects: Rectal irritation, abdominal cramps and diarrhoea. important cautions: Rectal use only for suppository formulations. Avoid if bowel obstruction is suspected; persistent rectal bleeding or severe pain requires assessment.

Phosphates

drug class: Rectal phosphate laxative/enema. uses: Rapid, short-term relief of constipation or bowel evacuation when indicated. side effects: Rectal discomfort, diarrhoea, dehydration and electrolyte disturbances. important cautions: Can cause serious phosphate, calcium and kidney complications, especially in older adults, dehydration or renal impairment. Do not exceed the product dose or repeat doses without medical advice; avoid in suspected obstruction.