old age & drugs
TRANSCRIPT
Old age & Drugs
Dr. Nidhi Maheshwari
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• Elderlies 12 treatment/year • patients < 45 5treatment/year
• 13% of total population
• 33% of all prescription drugs
• By 2040, represent 25% of total population, Consume 50% of all prescription drugs.
• Pk-pd changes• Non-compliance• Multiple medications• Self medication• Drug interactions
Pharmacokinetic changes
• ↓ hepatic blood flow & ↓ metabolising enzymes• Eg. Haolthane,• Diazepam
• ↓ renal function• Aminoglycosides- dose ↓ (1 to 0.75 to 0.5), duration ↓ ( to one/day)• Infusing vancomycin over 2 hrs (90 % excretion from kidney)
• Baroreflex sensitivity ↓ - postural hypotension marked• ↑ prostate gland mass Avoid anticholinergic action
CumulativeToxicity
Pharmacodynamic changes
• ↑ sensitivity of opioid receptors sufentail, alfentanil, fentanyl are twice potent.
• Receptor changes– Change in receptor numbers
– Changes in receptor affinity.
– Post receptor alteration
• ↓ response to β2 agonists may require higher doses of Salbutamol• ↓ anti HT action of β2 antagonists, ↑ antiHT action of CCBs and Diuretics
Non- compliance
• Multiple drugs together• Forgetfulness• Mood changes• Difficulty in swallowing
Use of multiple medications
• Herbal medications or uncoventional medications-history not asked
• eg. Ginkgo biloba extract-warfarin causes bleeding
• St. John’s wort with Serotonin reuptake inhibitors- Serotonin syndrome
• garlic
Self medications
Drug interactions
• venlafaxine and propafenone-hallucinations and psychomotor agitation
• Sodium valproate and levetiracetam-psychic disturbances
• phenobarbital and lamotrigine-blood dyscrasias
• Warfarin + selective & non-selective NSAIDs or SSRI’s or Omeprazole or lipid lowering agents or amiodarone/fluorouracil--- bleeding
• Cotrimoxazole-hypoglycemic 6 times
• Digoxin + clarithromycin digoxin toxicity raised 12 times more
• K+ sparing diuretics-hyperkalemia 20 times more
• Lithium with thiazides --reduce dose of lithium in elderlies or replace
• Carmazepine or valproic acid is preferred
• Avoid antipsychotics + antidepressants
• Antacids decrease in urinary acid secretion – increase in urine pH – reduction in salicyclate levels esp. in pt. on chronic aspirin treat.
Prescribing cascade• Cholinesterase inhibitors
(donepezil, rivastigmine, galantamine)-S/e diarrhoea, urinary incontinence---Rx-anticholinergics
• Antipsychotics or metoclopramidesymptoms of parkinsonismstarted on anti-parkinsonism s/e orthostatic hypotension, delirium
Criteria’s
• Beer criteria’s-to assess inappropriate drug prescribing
• STOPP-screening tool of older person’s prescriptions
• Drug burden index• FORTA-Fit for the aged
Cont…..
• Doxy with lots of water-prevent ulcers• To avoid osteoporosis –Use glucocorticoids with calcium and vit D• To prevent gastric acidity-H2 anatagonists• Prefer thiazides in minimum effective dose or with K sparing diuretic• Prefer B1 blocker, ACEI, ARBs, CCBs• Absorption of many drugs may be impaired – gastric acidity & function
exc. Acid labile erythromycin• Avoid ppnl, , thiazide diuretics in higher doses• Frequent thiazides-high dose-hypokalemia, hyperuricamia,
hyperglycemia• Hyperkalemia esp. With potassium sparing diuretics
• Reduce dose-Lignocaine, lithium, quinidine, aminoglycoside, digitalis
• Raise interval- Digitalis, aminoglycoside
• Assess clinically-atenolol, diazepam
• TDM frequently-Phenytoin, theophylline (dose adjustment)
• Avoid drugs with anticholinergic and hypotension as side effects
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• NSAIDs-May cause GI bleed and renal damage• INDOMETHACIN- CNS side effects• Naproxen-piroxicam-cumulative toxicity• Ibuprofen, nimesulide, cox-2 inhibitors may be prefered
• Digoxin, Beta agonists, Beta blockers - Less effect
• Better response-Ca blockers, ACE-I, diuretics• Ppnl-ppt asthma, pvd, chf-common in elderlies• Ppnl-BA and t1/2 increases with age• Prefer aspirin or clopidogrel over dipridamole as antiplatelet
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• Digitalis
• Reduction in clearance & little reduction in Vd may increase T1/2 > 50 %
• Renal function test should be done prior starting Rx• Frequent checking of electrolytes increase risk of arrythmias• ADR-Warfarin, Digoxin, Insulin, Oral antiplatelets, hypoglcemics