Prescription Medicines Flashcards
Allopurinol indication and dosage
Gout treatment and prevention of progression
100mg OD, increasing by 100mg every 4 weeks until target serum urate is reached (<0.36mmol/L)
Allopurinol mechanism of action
Inhibits xanthine oxidase, reducing the production of uric acid
Allopurinol adverse effects
Hypersensitivity syndrome
Severe idiosyncratic rection (skin reaction, eosinophilia + multi-organ involvement) - usually within 2-6 weeks of initiation. Associated with thiazide diuretics
Allopurinol interactions and contraindications
Azathioprine - avoid concurrent use. If cannot be avoided, use 1/3 to 1/3 of azathioprine dose
Mercaptopurine - DO NOT USE
Both cause bone marrow toxicity
Allopurinol precautions + safety in special populations
Prior to initiation consider testing for HLAB*5801 in selected patients (Koreans with Stage or worse CKD, Han Chinese + Thai irrespective of renal function)
Dose adjustment required in renal impairment
Reduce dose in hepatic impairment
Allopurinol advice and self-care
Monitor serum urate levels every 4 weeks until the target level is reached. Then blood tests every 3-6 months to check serum urate levels and kidney function
Take with food and a large glass of water
Encourage exercise, staying hydrated, caffeinated drinks, low-fat milk products and a good diet
Avoid lots of red meat, alcohol and sugary drinks
Amiodarone indication and dosage
Rhythm control
200mg TDS for 1 week, then 200mg BD for 1 week then 200mg OD. Titrate to the lowest effective dose
Amiodarone mechanism of action
Potassium channel blocker in cardiac tissues prolongs the refractory period so the cell is less excitable
Metabolised by CYP3A4 and CYP2C8
Absorption and bioavailability are variable between people
Amiodarone interactions and contraindications
Avoid drugs that also increase the chance of QT prolongation
Contraindicated Iodine sensitivity
CYP drugs
Amiodarone adverse effects
Photosensitivity, blue-grey skin discolouration, blurred vision, dry eyes, thyroid toxicity, pulmonary fibrosis, arrhythmias, increased LFTs
Amiodarone precautions and safety in special populations
Use with caution in hepatic impairment (risk of accumulation and toxicity)
Amiodarone advice and self-care
Pulmonary function and electrolyte (potassium) tests should be performed prior to initiation
LFT and thyroid function tests should be performed before treatment and every 6 months thereafter
Protect yourself from sunlight
Contact your doctor if experiencing cough, difficulty breathing, or feeling unwell that you can’t explain
Grapefruit juice may interfere with the medication
Colchicine indication and dosage
Acute gout and short-term prophylaxis
Acute: initially 1mg, followed by 500mcg 1 hour later (max 1.5mg per course)
Short-term prophylaxis: 500mcg once or twice daily for 3-6 months while urate-lowering therapy is introduced.
Max 2.5mg in 24 hours, 6mg over 4 days
Colchicine mechanism of action
Binds to tubulin during mitosis, inhibiting phagocytosis and causing cell death.
Does not decrease urate production, increase renal urate excretion or possess any analgesic properties
Colchicine adverse effects
NARROW THERAPEUTIC INDEX
Early warning signs: nausea, vomiting, abdominal pain, diarrhoea
Delayed symptoms (24-72 hours after indigestion): tachypnoea, electrolyte disorders, hypovolemia, haematological effects, seizure, shock, coagulopathy….
Colchicine interactions and contraindications
CYP3A4 and P-glycoprotein inhibitors (statins, azole antifungals, macrolides, grapefruit juice)
Chemotherapy agents have an additive effect on cell division
Colchicine precautions and safety in special populations
Renally cleared - dose adjustment may be required
Avoid if CrCl <10mL/min
Use with caution in GI and cardiac conditions
Dabigatran indication and dosage
Stroke, AF, TIA, HF, VTE
Typically 150mg BD
In DVT/PE treatment: starts after 5 days of heparinisation
Dabigatran adverse effects
Dyspepsia, nausea, diarrhoea, abdominal pain, dysphagia
Dabigatran interactions and contraindications
Ketoconazole, quinidine and clarithromycin increase the concentration of dabigatran (increasing the risk of bleed)
Amiodarone and verapamil contraindicated. If needed, reduce the dose of dabigatran or dose at different times of the day and monitor closely
Rifampicin, St John’s wort, phenytoin and carbamazepine reduce the efficacy of dabigatran
Dabigatran precautions and safety in special populations
Renally cleared - CrCl 30-50 reduce to 110mg
Do not give if below 30mL/min
In the elderly (75-80) reduce the dose to 110mg BD regardless of renal function
Dabigatran advice and self care
Take with food and a large glass of water
Remain upright for at least 30 minutes after taking
Monitor for signs of bleeding
Avoid NSAIDs
Do not open capsules
Keep in foils until taking
Dabigatran mechanism of action
Competitive and reversible inhibition of thrombin (factor 2)
Essentially mops up thrombin and stops the process of clot formation.
Prodrug
Tetracyclines indication and dosage
Respiratory infections (chronic bronchitis, CAP), STIs, acne
Acne: Minocycline 100mg daily in 1-2 divided doses. Doxycycline 50-100mg OD. 4-6 months duration
CAP: Doxycycline 200mg stat then 100mg OD
Susceptible infections: 100mg BD (both)
Tetracyclines mechanism of action
Bind to 30s ribosomal subunit, inhibiting binding of amino acid tRNA, inhibiting protein formation required for cell division.
Broad spectrum bacteriostatic
Tetracyclines adverse effects
GI disturbances, calcium chelation, photosensitivity
May cause hypersensitivity reactions
Tetracyclines interactions and contraindications
Metal collators (binds to metal instead and decreases absorption)
Isotretinoin and oral vitamin A treatment (benign intracranial hypertension)
Tetracyclines precautions and safety in special populations
Monitor patients on anticoagulants
Neither require renal dose adjustment
Use with caution in hepatic impairment (hepatic metabolism)
Avoid in pregnancy/breastfeeding and children under 12
Tetracyclines advice and self-care
Take with food and a large glass of water
Remain standing for at least 30 minutes after taking
Swallow whole (oesophagitis)
Avoid dairy, metal-containing antacids and iron supplements for 2 hours
Protect yourself from sunlight
Enoxaparin indication and dosage
Prophylaxis of VTE, treatment of angina/MI, prevention of thrombus formation
Dose varies.
Prophylaxis: 20-40mg SC q24h
Treatment: 1-1.5mg/kg q12-24h