10 potentially life-threatening drugs Flashcards by Roksana Świderska

What’s the problem with the following combination:

Methotrexate + Trimethoprim

Methotrexate and trimethoprim

Problem: Both drugs block DHFR

(dihydrofolate reductase that is needed for the production of follicle acid that is needed for RNA and DNA synthesis)

Consequence: Severe bone marrow depletion

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What’s the problem with the following combination?

Allopurinol + Azathioprine

Allopurinol + Azathioprine

Problem: Allopurinol inhibits xanthine oxidase (normally converts 6-mercaptopurine to thiouric acid)

6-mercaptopurine causes bone marrow supression

Consequence: severe bone marrow depression

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Enzyme inhibitors mnemonic

SICKFACES.COM

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Enzyme inducers mnemonic

CRAP GPs

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What’s the problem in the combination of

Verapamil (CCB) + beta-blocker

Verapamil + beta-blocker

Problem: severe bradycardia as SAN and AVN is inhibited

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What drugs and why can contribute to lithium toxicity?

Mechanisms of Lithium toxicity

1) Lithium is monovalent cation → similar structure to sodium

Drugs that reduce the absorption of Na+ → increase absorption of lithium (potential toxicity)

2) Drugs that decrease eGFR → reduce sodium excretion

thiazide diuretics
ACE inhibitors
NSAIDs

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Potential problem with Ciprofloxacin

Ciprofloxacin

may lower seizure threshold

Consequence: grand-mal seizure

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Potential problem with Gentamycin

Gentamycin is aminoglycoside → potential for acute nephrotoxicity

requires strict monitoring

*Gentamycin is used for gram -ve infections

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Drugs requiring strict monitoring

aminoglycosides (e.g. Gentamycin)
Teicoplanin
Vancomycin
Digoxin
Theophylline
Phenytoin
Carbamazepine

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What types of antibiotics (apart from Penicillins) we should avoid in a patient with penicillin allergy?

Co-amoxiclav (augmentin)
Tazocin (piperacillin)
Cephalosporins
Carbapenems

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What’s wrong with the combination of TCAs + MAOi?

TCA + MAOi

hypertensive crisis

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What’s the danger with Vincristine?

Vincristine CANNOT be given intrathecally as it’s highly neurotoxic → death

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SEs of corticosteroids therapy

Mnemonic → CUSHINGOID

Cataracts

Ulcers

Skin – striae/thin/bruised

Hypertension/hyperglycaemia, Hirsutism

Infection

Necrosis (femoral head)

Glycosuria

Osteoporosis/Obesity

Immunosuppression

Diabetes

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Mnemonic for TB drugs

PRIEST

Pyrazinamide

Rifampicin

Isoniazid

Ethambutol

STreptomycin

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Mnemonic for the presentation of serotonin syndrome

HARM

Hyperthermia

Autonomic instability

Rigidity

Myoclonus

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SEs of TCAs

(mnemonic)

TCAs - Side Effects

Thrombocytopenia

Cardiac (arrhythmia, MI, CVA)

Anticholinergic

Seizures

Mnemonic for anticholinergic SEs

Anticholinergic SEs → ABCD

Anorexia

Blurry vision

Constipation/Confusion

Dry mouth

Mnemonic for SEs of sodium valproate

VALPROATE

V - valproate
Appetite increase → weight gain
Liver failure → monitor LFT during 1st 6/12
Pancreatitis
Reversible hair loss – grows back curly
Oedema
Ataxia
Teratogenicity; Thromobocytopaenia
Encephalopathy (due to increased ammonia); Enzyme inducer

Classes and examples of anti-arrythmics

Sodium (Class I)

Ia Quinidine

Ib Lidocaine

Ic Flecainide

Beta Blockers (Class II) - propranolol

Potassium (Class III) - amiodarone

Calcium (Class IV) – verapamil

Mnemonic for contraindication to ACE inhibitors

‘PARK’

Pregnancy

Allergy

Renal artery stenosis

K+ increase and decrease in Na+ → decrease in BP

Mnemonic for contraindications/cautions for beta-blockers

Beta Blocker C.I./Cautions

ABCDE

Asthma

Block (heart block)

COPD

Diabetes Mellitus

Electrolyte imbalance (hyperkalaemia)

Mnemonic for contraindications for Warfarin in AF

C.I. to Warfarin in AF

‘AF Bleeds Horrendously’

Adherence poor
Falls history/risk
Bleeding/coagulation disorders
Hypertension

Mnemonic for contraindications to NSAIDs

Contraindications to NSAIDs

BARS

Bleeding (peri-operative, coagulopathy)

Asthma (10% sensitive to NSAIDs)

Renal disease

Stomach (peptic ulcer disease/gastritis)

Short mnemonic for enzymes inducers

Enzyme Inducers

‘PC BRAS’

Phenytoin

Carbamazepine

Barbiturates

Rifampicin

Alcohol (chronic)

Sulphonylureas

Drugs that may induce **nephrotoxicity by biochemical changes** (3 types of changes)

* **Increased Potassium** (*K supplements, K sparing diuretics, Ispaghula husk)* * **High Sodium Content** (*antacids)* * **Excessive Vitamin D replacement** *(alphacalcidol)*

(2) types of drugs that may induce nephrotoxicity by causing pre-renal damage

* **NSAID** → renal underperfusion (prostaglandin inhibition – afferent arteriole constriction) * **ACE inhibitors** → if already under perfusion due to renal artery stenosis **** NB care **ACEI and NSAID together** → acute underperfusion and AKI

What drugs and why can cause nephrotoxicity by post-renal damage?

* **Crystalluria** → obstruction: * - high dose sulphonamides* * - acetazolamide* * - methotrexate* * **Urinary retention** * -Anticholinergics eg TCAs* - alcohol

Drugs causing nephrotoxicity by intra-renal damage

* **_Hypersensitivity reactions_** - **Glomerular damage** *→ penicillamine, gold, aptopril, phenytoin, penicillins, sulphonamides and rifampicin* - **Interstitial nephritis** → *penicillins, cephalosporins, sulphonamides, thiazide diuretics, furosemide, NSAIDs and rifampicin)* * **_Acute tubular necrosis_** – **direct toxicity to tubule** → *aminoglycosides, amphotericin and ciclopsorin*

Are ***cephalosporins*** nephrotoxic?

**Cephalosporins:** * older ones directly toxic * some 3^rd generation eg *cefixime* - rarely nephrotoxic

Can analgesics be nephrotoxic?

* **NSAIDs →** AKI due to hypoperfusion and interstitial nephritis as well as analgesic nephropathy * Combinations of **paracetamol and /or aspirin** → reversible analgesic nephropathy

What can lithium cause?

Lithium – nephrogenic diabetes insipidus

Principles of prescribing in renal impairment

* Avoid nephrotoxic drugs wherever possible * Dose adjustment for CKD – depends on stage * Dialysis can remove some drugs * Some drugs just need dose adjustment according to CKD stage. Some need precise adjustment as narrow therapeutic/side effect window * Total daily dose adjusted : - Reduce size of individual dose or - Increase interval between doses

Drugs to be careful about in CKD

* Antibiotics * H2 receptor antagonists * Digoxin * Anti convulsants * NSAID’s