old age & drugs

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