• Indications: Constipation, bowel prep for procedures, surgery.

Pharmacodynamics (PD) Molecular Target

• Acts on the smooth muscle (bowel wall) of the colon, stimulating peristalsis and fluid secretion.

PD Physiological Effect

• Increases bowel movement and water secretion, softening stool.

Key Pharmacokinetics

• Absorption: Minimal.

• Distribution: Does not significantly distribute systemically due to minimal absorption.

• Metabolism: Prodrug = Converted to active form in the colon.

• Excretion: Mostly in feces.

Contraindications

• Acute abdominal conditions (e.g., appendicitis, obstruction), Hypersensitivity, Severe dehydration

Cautions

• Electrolyte imbalances, chronic use risks.

• Use cautiously in pregnancy and lactation.

• Not to be used by children under 6

Drug-Drug Interactions

• Risk of electrolyte imbalances with diuretics and corticosteroids.

• Antacids can increase bisacodyl absorption.

Adverse Effects

• Common: Abdominal cramps, diarrhea, bloating.

• Serious: Electrolyte imbalances, colonic dependence, rectal bleeding (though rare)

Monitoring

• Electrolytes (mainly potassium), hydration status, bowel function.

Dosing Regimen

• Oral: 5-10 mg daily.

• Suppository: 10 mg daily.

Clinical Practice Considerations

• Short-term use only, educate on hydration and lifestyle changes to avoid dependence.

Gastric acid suppression: Proton pump inhibitors (omeprazole)

Drug Classification & Name

• Class: Proton Pump Inhibitor (PPI)

• Drug Name: Omeprazole

• Indications:

  • Gastroesophageal reflux disease (GERD)

  • Peptic ulcer disease (PUD)

  • Helicobacter pylori eradication (part of triple therapy)

  • Zollinger-Ellison syndrome (excess stomach acid)

  • Prevention of NSAID-induced ulcers

Pharmacodynamics (PD): Molecular Target

• Target: Hydrogen/Potassium ATPase (proton pump) in gastric parietal cells

Pharmacodynamics (PD): Physiological Effect

• Irreversibly blocks acid production, reducing stomach acidity and promoting ulcer healing

Key Pharmacokinetics

• Absorption: Well absorbed in the small intestine

• Metabolism: Liver (CYP2C19, CYP3A4 enzymes)

• Half-life: 1–2 hours, but effects last 24+ hours

• Excretion: Mostly in urine and feces

Contraindications

• Allergy to omeprazole or other PPIs

• Severe liver disease

• Concomitant use with rilpivirine (HIV drug)

Cautions

• Long-term use may cause vitamin B12 deficiency

• Risk of osteoporosis and fractures

• May increase risk of gut infections (C. difficile)

• Caution in kidney disease

Drug-Drug Interactions

• Reduces absorption of drugs needing stomach acid (e.g., ketoconazole, calcium carbonate, iron supplements)

• Increases blood levels of warfarin, diazepam, and phenytoin (CYP2C19 inhibition)

• May reduce the effect of clopidogrel (antiplatelet drug)

Adverse Effects

• Common: Headache, nausea, diarrhea, constipation, flatulence

• Serious but rare: Kidney disease, low magnesium, fractures, gut infections

Monitoring

• Check vitamin B12 levels in long-term users

• Bone health monitoring in older adults

• Magnesium levels in long-term therapy

• Kidney function tests for prolonged use

Dosing Regimen

• GERD & ulcers: 20–40 mg once daily

• H. pylori eradication: 20 mg twice daily (with antibiotics)

• Zollinger-Ellison syndrome: 60 mg once daily, adjust as needed

Important Clinical Practice Considerations

• Use lowest effective dose for the shortest time

• Taper gradually if stopping after long-term use to prevent acid rebound

• Advise calcium & vitamin D supplementation for long-term users

• Assess for drug interactions in patients on multiple medications

Class & Indications:

5HT3 receptor antagonists - Used for nausea/vomiting due to chemotherapy, radiotherapy, or surgery.

PD Molecular Target:

Blocks 5HT3 receptors in the chemoreceptor trigger zone and gastrointestinal tract.

PD Physiological Effect:

Reduces nausea and vomiting by inhibiting serotonin's effect.

Key Pharmacokinetics:

Absorption: Rapid, taken orally or IV.

Metabolism: Hepatic (CYP3A4).

Half-life: 3-4 hours.

Contraindications:

Hypersensitivity to ondansetron.

Cautions:

Risk of QT prolongation, especially with other QT-prolonging drugs.

Drug-drug Interactions:

Apomorphine (serious hypotension), other QT-prolonging agents (e.g., amiodarone).

Adverse Effects:

Headache, constipation, dizziness, QT prolongation.

Monitoring:

Monitor for QT prolongation in high-risk patients.

Dosing Regimen:

4-8 mg every 8 hours, can be increased for chemotherapy-induced nausea.

Important Clinical Practice Considerations:

Effective for acute nausea but not for long-term management.

• Naloxone: Opioid antagonist; used for opioid overdose reversal.

• Acetylcysteine: Mucolytic and antidote for acetaminophen overdose.

PD Molecular target:

• Naloxone: μ-opioid receptor antagonist.

• Acetylcysteine: Restores hepatic glutathione levels via its sulfhydryl group.

PD physiological effect:

• Naloxone: Competitive inhibition of opioid effects, reversing respiratory depression, sedation, and analgesia.

• Acetylcysteine: Reduces hepatotoxicity by detoxifying N-acetyl-p-benzoquinone imine (NAPQI), a toxic acetaminophen metabolite.

Key pharmacokinetics:

• Naloxone: Rapid onset (2-5 minutes IV), short half-life (30-80 minutes), requiring repeated dosing in long-acting opioid toxicity.

• Acetylcysteine: Administered IV or orally; metabolized in the liver with ~6-hour half-life. Best efficacy when given within 8-10 hours post-overdose.

Contraindications:

• Naloxone: None in emergency situations.

• Acetylcysteine: Hypersensitivity to acetylcysteine.

Cautions:

• Naloxone: Precipitation of acute opioid withdrawal in dependent individuals.

• Acetylcysteine: Anaphylactoid reactions when administered intravenously (rare).

Drug-drug interactions:

• Naloxone: No significant drug interactions but may diminish opioid analgesia.

• Acetylcysteine: No significant drug interactions reported.

Adverse effects:

• Naloxone: Nausea, vomiting, tachycardia, agitation, withdrawal symptoms.

• Acetylcysteine: Nausea, vomiting, rash, flushing, or anaphylactoid reactions.

Monitoring:

• Naloxone: Reassess respiratory rate, oxygen saturation, and level of consciousness frequently.

• Acetylcysteine: Monitor serum acetaminophen levels, liver function tests (ALT, AST, bilirubin). Watch for hypersensitivity reactions.

Important clinical practice considerations:

• Naloxone: Ensure adequate airway management; anticipate prolonged care for long-acting opioids.

• Acetylcysteine: Effective when given early. Include close observation for signs of overdose progression and hepatic failure.