Pharmacology

Nurses must always give the; the correct dose of the correct drug to the correct patient at the correct time via the correct rout

Drug

Many drugs are chemical substances, natural or synthetic, which are introduced deliberately into the body to bring about a physiological change.

Give examples of physiological change

Other drugs are designed not to bring about any physiological change

Which drugs are derived from natural products?

Which drugs are derived synthetically?

Drugs may be used for; cure, improvement, diagnosis, prophylaxis

Drug effects aid diagnosis

E.g. antacids, glyceryl trinitrate

Symptomatic treatments

E.g. antidiarrhoeals, antipyretics, analgesics, steroids, NSAIDs, antacids

Treatment of cause

E.g. antibiotics, antifungals

Terms

Prescribed drug

Drug of abuse/recreation

Indication

Contra-indication

Side effect

ADRs

Special precaution

Interaction

Potentiation

Dose

Route

Toxic effect

Tolerance

Compliance

Measurements

Metric system; Deci 1/10 Centi 1/100 Milli 1/1 000 Micro 1/ 1 000 000

Volume 1 ml = 1 cm3 100ml = 1 cl 1, 000ml = 1 l

Concentration

Usually mg per ml

Units of concentration are moles, (1 mole is the number of atoms in 12 g of carbon, a molar solution is that number of molecules in 1 litre of pure H₂O)

A millimole is one thousandth of a mole 1,000 mmol = 1 mole

Some drugs are measured in international units; eg insulin is 100 iu per ml

Routes of administration

Drugs may be given for a local or a systemic action

What is the purpose of giving a drug for systemic effect?

Give examples of drugs given for a local effect?

Drugs may be given via an enteral route, i.e. via the GI tract

Drugs may be given via a parenteral route, i.e. not via the GI tract

Decide if these routes are local or systemic, enteral or parenteral

Oral Nasogastric or PEG

Per rectum Sublingual

Intravenous bolus Intravenous infusion

Intramuscular Subcutaneous

Intradermal Intrathecal

Epidural Topically

Transdermal Inhalation

Injected into lungs Into eyes

Into ears Into nose

Into a joint Intracardiac

Pharmacokinetics

Barriers to absorption

Conditions at the site of the administration

Bioavailability

Therapeutic concentration

Therapeutic range

Titration

Factors effecting distribution

Factors effecting tissue concentration

Protein binding

Most drugs bind to albumin to some extent

Protein bound drug is inactive, `free` drug is active

Albumin levels are reduced in older people, liver failure and malnutrition

Drug excretion

Half life - the time it takes to lower the plasma concentration by half

Biotransformation metabolised drugs down into molecules which are easy to excrete

Liver is most important in catabolism

Enzymes for metabolism are also in the gut, lungs, kidney and blood

First pass metabolism

Drugs may be eliminated from the body via the kidneys, liver, bowel, lungs, exocrine glands

Enzyme inhibitors - cimetidine, erythromycin

Enzyme inducers - phenytoin, carbamazepine, rifampicin, St. John`s Wort, alcohol, smoking

Implications for breast feeding

Implications for the elderly

Adverse reactions

Type A Predictable Dose dependent

Type B Unpredictable Not dose dependent

Iatrogenic

Teratogenic

Allergic

Common reactions include, urticaria, rash, puritus, rhinitis

Anaphylactic reactions

Which groups of drugs may cause the following unwanted effects?

Bleeding Bradycardia

Hypotension Respiratory depression

Constipation Bone marrow depression

Drugs and the elderly

Drug interactions which slow absorption

Avoid polypharmacy

Antacids contain magnesium, calcium and aluminium ions that can form insoluble complexes with other drugs

Protein binding

Free fractions of drug may have therapeutic or toxic effects, protein bound drug is inactive.

Albumin production declines with age

Eg. phenytoin, aspirin, tolbutamide, naproxen and warfarin are normally highly protein bound

Slowed metabolism in the liver

With age hepatic circulation and function decline

Drugs normally catabolised in the liver will have a longer half life

Eg. benzodiazepines are broken down in the liver and the metabolites excreted by the kidneys

Reduced renal function

Renal function also declines with age

Eg, aminoglycoside antibiotics, (mycin) rely in the kidneys for excretion, they have high nephrotoxicity and ototoxicity

Altered end organ effects

Pharmacodynamics may change in older organs

Eg. older people have an increased sensitivity to anticholinergics

Applications

Gain drug history Monitor patients for effects