Routes of Administration of drugs

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Routes of Administration of drugs

• By.
• Dr.Abdul latif Mahesar

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• ROUTES OF ADMINISTRATION
• ?Enteral (Alimentary)
• ? Par - enteral
• ( Other than Alimentary)

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• ROUTES OF ADMINISTRATION
• Enteral (Alimentary canal)
• Oral
• Buccal Sublingual
• Rectal
• Nasogastric

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• Par - enteral ( Other than Alimentary)
• Par - enteral injections
• Intravenous , intramuscular, intradermal,
  Subcutaneous, intrarterial, intrarticular,
  intraperitoneal, intrathecal
• Inhalation
• Topical

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• ORAL
• MERITS
• Commonest, Safest
• Convenient ,
• No skill required, self medication
• Painless, acceptable
• Cost effective
• No maximal/strict sterilization required

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ORAL

• MERITS contd
• Due to slow rate of absorption adverse effects
  occurs less and slowly as compared to
• parenteral route
• Large volume (doses) can be given
• Systemic / local effects in G.I.T
• For local effect
• e.g.,
• neomycin (an aminoglycoside),
• anthelmintics
• antiamoebic.

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• ORAL cond
• De-merits
• Absorption varies (delay, decrease, or
• increase )
• affected by ---- food or drugs that
  affect GI
• motility
• e.g. antimuscarinic, opioids )
• (Dose may not accurately be delivered)
• Irritation of gastric mucosa
• Patient compliance not ensured

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• ORAL contd
• Demerits
• First pass metabolism ( First pass effect,
• Presystemic elimination)
• Metabolism of drug (to inactive form)
• after administration before it reaches
  the
• systemic circulation Usually with orally
  
• administered drugs

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• ORAL
• De-merits contd
• First pass metabolism
• - Orally administered drugs
• - First pass effect in GIT
• - Hepatic first pass
  metabolism
• during its first passage thru liver
• Greater the first pass effect, lesser will be
• the bioavailability

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• BIOAVAILABILITY
• is the fraction of administered drug that
• gain access to the systemic circulation
• (after absorption) in a chemically
• unchanged form

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• ORAL contd
• Demerits contd
• - Drugs with high first pass effect needs
  
• to be given in high doses
• - Variation in first pass effect
• among individuals cause variation in
  
• drug response

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• ORAL contd
• Demerits contd
• Not suitable for
• Unconscious patients
• Vomiting patients
• Emergency --- (Slow onset of action)
• GIT diseases or abnormality may
• affect the absorption of drug

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• ORAL contd
• Demerits
• - Following drugs can not be given by oral
  route
• - Drugs destroyed by Stomach pH
• (some Penicillins e.g., benzyl
  penicillin)
• - Drugs destroyed by Intestinal enzymes
  
• (e.g., Insulin, oxytocin)
• - Hydrophilic drugs which can not
  absorbed
• (e.g., Aminoglycosides, but can be given for
• local effect such as neomycin)

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• ORAL contd
• Demerits contd
• Uneven distribution (for local effect),
• in some diseases of gut whole thickness of
  wall is
• affected (e.g. severe bacillary dysentery,
  typhoid)
• effective blood concentrations ( as well
  as
• luminal concentrations ) may be needed.
• Drug interaction
• one drug can affect the absorption of
  other
• drug e.g., antacids decrease the
  absorption of
• tetracyclines.

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• SUBLINGUAL BUCCAL
• Merits
• Rapid onset of action
• useful in emergency
• (glyceryl trinitrate, nifedipine
  ergotamine),
• especially if tablet is crushed, giving
  greater
• surface area for solution
• Effect can be terminated by spitting out
  tablet

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• SUBLINGUAL BUCCAL
• Merits
• No sterilization required
• No skill
• first pass hepatic metabolism is avoided
• Increase in bioavailability
• Not affected by gastric acidity or intestinal
  enzymes

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• SUBLINGUAL BUCCal
• Demerits
• Inconvenient for frequent use
• Irritation of oral mucosa excessive
• salivation
• Promotes swallowing, so losing the
  advantage of
• bypassing the first pass effect
• Patient compliance not ensured
• Not suitable for large doses and vomiting
  patients
• Bitter, irritant can not be given

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• RECTAL
• Dose requirement same or slightly greater than
  
• oral route

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• RECTAL
• Merits
• Can be used for producing both the systemic
  effects
• and local effects
• Drugs that are irritant to stomach can be given
  by
• suppository (aminophylline, indomethacin)
• Suitable in unconscious, vomiting , motion
  
• sickness, migraine or when a patient can
  not swallow ,
• when cooperation is lacking (sedation in
  children)

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• RECTAL
• Merits
• No sterilization
• No skill
• Avoid 50 first pass hepatic metabolism (from
• lower rectum)
• For local effect e.g. in proctitis or colitis

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• RECTAL
• Demerits
• Psychological, patient may be embarrassed and
  dislike this
• way
• Irritation of mucosa inflammation may occur
• with repeated use
• Emergency (slow onset of action)
• Absorption unreliable, especially if rectum is
  full of
• feces

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• PAR-ENTERAL INJECTIONS
• Dosage forms
• Solution,
• Suspension

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• PAR-ENTERAL INJECTIONS
• Intravenous ( I / V ),
• Intramuscular ( I / M ),
• Subcutaneous ( S / C )
• Intra dermal
• Intra articular
• Intrathecal
• Intraperitoneal

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• I / V INJECTIONS INFUSIONS
• Merits
• Rapid onset of action
• useful in emergency
• No first pass effect, 100 bioavailability,
• Dose more accurately delivered give smooth
• effective, highly predictable blood
• concentration
• Suitable in vomiting , motion sickness,
  migraine,
• unconscious patients, or when a patient
  can not
• swallow , when cooperation is lacking
• - Large volume (doses) of drug can be given

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• Intra venous and I.V infusions contd
• Merits
• Suitable in vomiting , motion sickness,
  migraine,
• unconscious patients, or when a patient
  can not
• swallow , when cooperation is lacking
• Large volume (doses) of drug can be given

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Intra venous and I.V infusions contd

• Following drugs which can not be given by
• oral route, are given intravenously
• Drugs destroyed by stomach pH
• (some Penicillins e.g., benzyl
  penicillin)
• Drugs destroyed by intestinal enzymes
• (e.g., Insulin)
• Hydrophilic drugs which can not
  absorbed
• (e.g., Aminoglycosides)

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• Intra venous and I.V infusions contd
• Merits
• - Drugs that are too irritant (anticancer
  agents) to be
• given by other routes
• - In I.V. infusion ----Rapid modification of
  dose and
• immediate cessation of administration if
  unwanted
• effects occur

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• I / V INJECTIONS INFUSIONS
• De-merits
• Costly
• Inconvenient
• More chances of adverse effects, most
• dangerous
• Maximal Sterilization, chances of infection
• Skill, no self medication
• Local irritation at site of administration

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• I / V INJECTIONS INFUSIONS
• Demerits
• Local venous thrombosis with
• prolonged infusion
• irritant formulations
• microparticulate components of
  infusion
• fluids, especially if small veins are used
• Infection of intravenous catheter and small
  thrombi on its tip during prolonged infusions

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• PARENTERAL I / M INJECTIONS
• Merits
• Reliable and suitable for irritant drugs and
• depot preparations (penicillins ,
  neuroleptics,
• medroxyprogesterone) can be used at
  monthly
• or longer intervals
• Absorption is more rapid than following
• subcutaneous injection or oral route
• (soluble preparations are absorbed within 10
  30 mins.)

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• I / M INJECTIONS
• De-merits
• Inconvenient
• Painful especially for frequent use
• More chances of adverse effects than oral
• Sterilization,
• Chances of infection
• Skill required
• Local irritation at site of administration

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• I / M INJECTIONS
• De-merits
• Not acceptable for self administration
• If any adverse effect occur tha can not be
• removed.

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• S / C INJECTIONS
• Merits
• Can be used for local and systemic effects both
• Reliable and acceptable for self administration
• (e.g. diabetic patients taking Insulin)
• For local effect --- e.g. local anesthetics

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S / C INJECTIONS

• De-merits
• Poor absorption in peripheral circulatory
• failure
• repeated injections at one site can cause
• lipodystrophy, resulting in erratic
• absorption (insulin)

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• INHALATION
• Can be used for local systemic effects
  both
• As a gas, --- e.g. ---- General
  anaesthetics
• As an aerosol,--- e.g. ---- ß2
  adrenoceptor agonist
• 
  bronchodilators
• As a powder, e.g. sodium chromoglycate

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• INHALATION
• Merits
• Drugs as gases can be rapidly taken up or
  eliminated,
• giving the close control that has marked
  the use of
• this route in general anesthesia
• Self administration is practicable
• Aerosols powders provide high local
  concentration
• for action on bronchi, minimizing
  systemic effects
• Aerosols can also be used for systemic effect,
  e.g
• ergotamine for migraine

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• INHALATION
• De-merits
• Special apparatus is needed
• Drug must be nonirritant.
• If the patient is unconscious
• Obstructed bronchi (mucus plugs in asthma) may
  
• cause therapy to fail

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• TOPICAL application
• For local effect
• Skin
• Mucous membrane (eye, nose , ear , lungs,
  
• anal canal, rectum, urethra, vagina, etc.
  )
• For systemic effect ----- Transdermal

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• TOPICAL APPLICATION FOR LOCAL EFFECT
• Dosage forms
• Ointment, lotion, cream, etc
• Merits
• usually high local concentration can be used
• without systemic effect

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• TOPICAL APPLICATION FOR LOCAL EFFECT
• Demerits
• systemic effects can occur especially when
  there is
• tissue destruction e.g.,
• adrenal steroids neomycin --- to ----
  skin,
• atropine ß-adrenoceptor blocker ---
  to --- eye

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• TOPICAL APPLICATION FOR SYSTEMIC EFFECT
  TRANSDERMAL DELIVERY SYSTEM (TDS)
• Dosage form
• Patches, ointment
• as a sticking plaster (Patch) attached to
  skin or
• as an ointment
• glyceryl trinitrate
• postmenopausal hormone
  replacement

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• TOPICAL APPLICATION FOR SYSTEMIC EFFECT
• Merits
• Used for slow continuous administration for
  long
• duration
• Fluctuations in plasma concentration are
  largely
• avoided
• Usually No first pass effect
• Drug can be removed if required

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• TOPICAL APPLICATION FOR SYSTEMIC EFFECT
• Demerits
• Only small number of drugs can be used by
• this route
• Slow onset of action
• Local reactions