Top 100 Drugs III Flashcards
In what state and where is iron best absorbed?
Fe2+ (ferrous state)
Duodenum and jejunum
Give 2 drugs that iron reduces absorption of?
Bisphosphonates
Levothyroxine
What are examples of bulk-forming laxatives?
Ispaghula husk
Methylcellulose
Sterculia
What are the major side effects of bulk-forming laxatives?
Mild abdominal distension
Flatulence
Faecal impaction
Bowel obstruction
What are examples of osmotic laxatives?
Lactulose
Macrogol
Phosphate enema
What are the indications for lactulose?
Constipation and faecal impaction
Bowel preparation prior to surgery/endoscopy
Hepatic encephalopathy
What conditions must phosphate enemas be used with caution?
Heart failure
Ascites
Electrolyte disturbances
(causes significant fluid shifts)
What are examples of stimulant laxatives?
Senna
Bisacodyl
Glycerol suppositories
Docusate sodium
When are stimulant laxatives contraindicated?
Bowel obstruction
What is the mechanism of action of lidocaine?
Blocks voltage-gated sodium channels
What are the indications for lidocaine?
- Local anaesthetic
- Antiarrhythmic drug in VT
- VF refractory to electrical cardioversion (although amiodarone more commonly used)
What are indications for macrolides?
- Respiratory and skin/soft tissue infection treatment where penicillin C/I due to allergy
- Severe and atypical pneumonia
- Triple therapy for H.pylori eradication
What is the mechanism of action of macrolides?
Blocks 50S ribosome
Prevents translocation
Inhibits protein synthesis
BACTERIOSTATIC
What are the major side effects of macrolides?
Irritant effects Abx- associated colitis Cholestatic jaundice QT prolongation Ototoxicity (high doses)
What drugs must macrolides be used in caution with?
- Drugs that require P450 metabolisation since macrolides (erythromycin and clarithromycin inhibit P450).
E.g. warfarin, statins. - Drugs that prolong QT interval e.g. antipsychotics, SSRIs, amiodarone, quinine, quinolones
What are the important adverse effects of metformin?
GI upset
Lactic acidosis
When is metformin contraindicated?
Severe renal impairment
Withhold acutely in AKI, severe tissue hypoxia, acute alcohol intoxication, hepatic impairment
How long prior to IV contrast injection must metformin be withheld for?
48 hours
What are the indications for methotrexate?
- DMARD
- As part of chemotherapy for leukemia, lymphoma and solid tumours
- Severe psoriasis
What is the mechanism of action of methotrexate?
Inhibits dihydrofolate reductase (prevents conversion of folic acid to tetrahydrofolate)
What are important adverse effects of methotrexate?
Mucosal damage Myelosuppression Hypersensitivity reactions Hepatitis, pneumonitis Cirrhosis and pulmonary fibrosis (long-term)
Give 2 other examples of folate antagonists asides from methotrexate?
Don’t prescribe in combo with methotrexate!
Trimethoprim
Phenytoin
What is the methotrexate dosing regimen for autoimmune disease treatment?
7.5-20mg ONCE WEEKLY!
+ folic acid supplementation
What are the indications for metronidazole?
Abx- associated colitis Oral infections Aspiration pneumonia Surgical and gynaecological infections caused by anaerobes Protozoal infections e.g. dysentery
What are the long-term neurological side effects associated with metronidazole use?
Optic neuropathy
Seizures
Encephalopathy
Why does metronidazole + alcohol cause a disulfiram-like reaction?
Metronidazole inhibits acetaldehyde dehydrogenase, which is needed to clear acetaldehyde (intermediate metabolite) from the body
What are the features of a disulfiram-like reaction?
Flushing
Headache
N&V
What drugs may reduce efficacy of metronidazole?
P450 inducers
e.g. phenytoin, rifampicin
When is naloxone indicated?
Treatment of opioid toxicity (associated with respiratory or neurological depression)
What is the mechanism of action of naloxone?
Competitive antagonist of opioid-u receptors, only works in the presence of exogenous opioids
What adverse effects may naloxone cause?
Opioid withdrawal reaction in opioid dependent patients:
Pain, restlessness, nausea, vomiting, dilated pupils, cold and dry skin with piloerection
When is nicorandil indicated?
Prevention and treatment of chest pain in stable angina
What is the mechanism of action of nicorandil?
Arterial and venous vasodilatation
Through its actions as a nitrate and activating K+ATPase channels
Efflux of K+ leads to hyperpolarisation, reduced intracellular Ca2+ and reduced smooth muscle contraction
In what conditions is nicorandil contraindicated?
LVF
Hypotension
Pulmonary oedema
What is the mechanism of action of varenicline?
Partial nicotinic receptor agonist
Reduces withdrawal symptoms and the rewarding effects of smoking
What is the mechanism of action of buproprion?
Inhibits reuptake of noradrenaline or dopamine in the synaptic cleft
Give an example of a short acting and long acting nitrate?
Short acting - GTN
Long acting - ISMN
What are common SEs of nitrates?
Flushing Headaches Light-headedness Hypotension Tolerance with ISMN
What are the major contraindications for nitrate use?
Severe aortic stenosis
Haemodynamic instability
What is the mechanism of action of NSAIDs?
COX inhibitor
Reduces prostaglandin synthesis
Main adverse effects of NSAIDs?
GI toxicity + ulceration Renal impairment CV events Hypersensitivity reactions Fluid retention
What gastroprotection prescribed with an NSAID?
Lansoprazole 15mg daily
What are the important adverse effects of OCP/HRT?
Irregular bleeding Mood changes VTE Cardiovascular disease Increased risk of breast and cervical cancer
Concurrent use of P450 ______ reduces efficacy of contraception?
Inducers
e.g. rifampicin
What are the indications for co-codamol?
Mild to moderate pain
What is co-codamol and co-drydamol composed of?
Paracetamol + codeine/dihydrocodeine
What are the side effects of co-codamol and co-drydamol?
In normal doses- Nausea, constipation, drowsiness
In overdose- hepatotoxicity, respiratory and neurological depression
What are the indications for strong opioids?
- Rapid relief of acute severe pain
- Relief of chronic pain when other drugs on the ladder are insufficient
- Relief of dyspnoea in palliative care
- Relief of dyspnoea and anxiety in acute pulmonary oedema
What is the mechanism of action of opioids?
Blocks mu receptors in CNS
Reduces neuronal excitability and pain transmission
Blunts response to hypoxia and hypercapnia in medulla (reduces respiratory drive and breathlessness)
Reduces sympathetic nervous system activity
What are the major adverse effects of opioids?
Respiratory depression Neurological depression N&V Pupillary constriction Constipation Itching Tolerance and dependence Withdrawal reaction
In what conditions should opioid doses be reduced?
Renal impairment
Hepatic failure
Elderly
