Iourntl] of the Axrnerican Association for Laboratory Animal Science
`Copyright 2011
`by the American Aesociation for Laboratory Animal Science
`
`Vol 50. No 5
`September 2011
`Pages 500 613
`
`Administration of Substances to Laboratory
`Animals: Routes of Administration and
`
`Factors to Consider
`
`
`
`Patricia V Turner,“ Thea Bralab,2 Cynthia Pekovv,3 and Mary Ann Vasbinder‘
`
`Administration of substances to laboratory animals requires careful Consideration and planning to optimize delivery of
`the agent to the animal while minimizing potential adverse experiences from the procedure. For all species, many different
`routes are available for administration of substances. The research team and IACUC' members should be aware of reasons
`
`for selecting specific routes and of training and competency necessary for personnel to use these routes effectively. Once a
`route is selected, issues such as volume of administration, site of delivery, pH of the substance, and other factors must be
`considered to refine the technique. Inadequate training or inattention to detail during this aspect of a study may result in
`unintentional adverse effects on experimental animals and confounded results.
`
`AdJIIjnistration of substances to laboratory animals is often
`a critical component of experimental design. Administered
`substances may include: infectious disease agents; various
`therapeutics, such as vaccinations, antimicrobials, pharmaco»
`logic agents, anesthetics, and analgesics; chemical test agents;
`radiocontrast agents; electrolytes and other fluids; and nutritive
`support. Because substances may be administered repeatedly
`to the same animal or to multiple animals on the same study,
`the dosing methodology is an important consideration when
`planning an experiment and during protocol review by animal
`care and use committees and represents an essential opportunity
`for refining neannent of research subjects. Specific considera»
`tions for delivery of substances to animals are numerous and
`include factors such as absorption, distribution, metabolism
`and excretion of therapeutic or chemical agents; route, vol-
`ume. and frequency of administration; duration of treatment;
`pH, stability, homogeneity, and osmolality of the substance to-
`be administrated; selection of vehicle or solvent for delivering
`substances that cannot be admirdstered in a solid or particulate
`stateysoiution preparation, including considerations for sterility
`if the substance is being administered parenterally; and dosing
`apparatus and animal restraint necessary for specific routes of
`delivery. In addition, research teams should be aware of poten-
`tial adverse effects related to substance administration to avoid
`
`confounding effects with other aspects of study design and to-
`permit accurate interpretation of IESEBI'Cl'I findings.
`Although understanding the basic pharmacology of any
`administered therapeutic or chemical agent is important for
`experimental planning, it is beyond the scope of this article to
`review principles of ph armacokinetics and pharmacodyn amics,
`and readers are referred to several eXcellentteth dealing with
`these subjectsm “E195 This article is the first of a 2—part reviEW
`
`Rest-iced: 14 Der: 201i}. Revision requested: 26 Ian 2011.Accq1teri:21 Mrlflli.
`leHrlmenl qf Palkobiclogy, University of Guelph. Guelph. Conrado, impairment of
`Cormorant»: Medicine. School quedfrms, University of Washington and 3Rosmrdt and
`Development. Veterans Afinirs PugetSuuml fimiflr Care System, Seattle, Washington;
`iPlatform, Technology and Sciences. inlityonri Risk Marrtgorrrntfiloxn Smith Kline,
`Resurrth Margie Park, North Corcltmi.
`tor-responding author. Email; wtumn‘é’uogmlpltur
`600
`
`of substance delivery to laboratory animals and summarizes
`recommended practices for various routes of administration to
`a range of species and factors to consider during experimental
`planning. The second part of this review examines dosing
`equipment and apparatus needed for substance delivery, con-
`siderations for selecting vehicles, and solute preparation and
`handling.“
`
`Routes of Administration
`Selection ofa route. Substances are administered to laboratory
`animals by a wide variety of routes. A key Factor determining the
`route selected is whether the agent is being administered for a
`local or systemic (either enteral [through the digestive tract] or
`pa renteral [outside the digestive tra ct]) effect. Parenteral admin-
`istration methods typically produce the highest bioavailability
`of substances because these methods avoid the first—pass effect
`of hepatic metabolism, which occurs commonly with orally
`administered chemicals and therapeutics. Parenteral routes also
`circumvent some of the unpredictability associated with enters]
`absorptive processes. Furthermore, regulatory requirements
`may influence the selection of a particular route, dependinan
`thepurpose of'the study (for example, noncljnical safety testing,
`in which the route ofdeliver'y to animals should closely resemble
`the projected route of administration to humans}.3753
`A substance may be given into the mouth (ora fly] or deliv»
`cred directly into the stomach [gastric gavagej; delivered into
`a blood vessel (intravenous); delivered onto, into, under, or
`across the skin or into a muscle (cpicutaneous, intradermal,
`su bcutaneoue, transdermal, and intramuscular administta
`tion, respectively); instilled onto or into the eye [transcomeal
`or intraocular, respectively); into the brain (intracerebral) or
`the space surrounding the dura meter or that surrounding the
`distal spinal cord (epidural and intrathecal, respectively]; ad—
`ministered into the peritoneal cavity (mtraperitoneal), directly
`into the marrow cavity {intraosseous}; sprayed into the nose
`for absorption across the nasal mucous membranes or into the
`lungs (intranasal) or delivered into the lungs by direct tracheal
`instillation [intratracheali or inhalation; or administered by a.
`range of less com mon routes using other body orifices, surgical
`
`lnnoPharma Exhibit 1074,0001
`
`

`

`exposmes, and species-specific anatomic features (for examples,
`see references 16, 4], 60, 64, 73, 91, and 127).
`in laboratory species, many of the commonly used methods
`of delivery require lestraint, sedation, or general anesthesia.
`The use of such manipulations should be considered when
`Selecting the administration route to refme procedures so that
`they are less invasive or aversive to the animals. In addition,
`each route has advantages and disadvantages that should be
`considered depending on the final effect to be achieved, and
`ultimately the route selected will markedly affect the pharma~
`cokinetics of the substance. This pharm acokinetic effect of mu to-
`of adm inistration is exemplified by naloxone, a potent opioid
`antagonist. Given intravenously, naloxone rapidly reverses
`opioiddnduced-central nervous system depression,” but when
`given enterally, the drug can be used to treat opioid-induced
`bOWEl stasis without antagonism of the analgesic effects of
`systemically administered cpioids.52 Another consideration
`regarding once-daily administration of substances to animals
`is their chronobiology or- circadian rhythm. Depending on the-
`aims and objectives of the experiment, the timingr of substance
`ad ministration may need to be considered carefully, for example,
`to administer a therapeu tic when an animal 's system is most or
`least metabolically active to induce or minimum toxicitym
`Enter-a! administration. Administration of substances directly
`into the mouth, admixed in diet or other foodstuffs, or by oro-
`gastric or nasogastric gavage is Common in laboratory animal
`medicine and research Per rectum administration of substances
`
`by enema or suppository is less common in animals than in
`humans. The oral route is economical, convenient, relativer
`s'a fe, and some animals can be trained. to cooperate voluntarily,
`depending on the compound being administered (Figure ‘l A
`through C). Although voluntary consumption of the material
`being administered is ideal, this dosing technique may not be
`reliable in. all animals or dose groups or For long-term studies,
`because of individual preferences for flavors, palatability is-
`sues, and changes in behavior over time. For substances being
`tested for safety, oral dosing mimics the most commonly used
`mode of administration of substances to humans. When placing
`substances directly into the mouth, it is important to ensure that
`tablets or gelatin capsules containing test material are placed
`far back in the mouth and that the animal sWallows, to ensure
`receipt of the full dose. The number and size of capsules or
`tablets administered should be proportional .to the size of the-
`animal being closed, to minimize regurgitation. (Savage (es-
`ophageal or gastric) is often used in research settings, instead
`of mixing substances in water or food, to ensure precise and.
`accurate dosing of animals (Figure 1 D).
`Selection of appropriate tubing size for orogastric or na—
`sogastric gavage is important to minimize discomfort while
`optimizing delivery of substances. Nasogastric tubes are used
`commonly in rabbits for enteral nutrition and in nonhuman
`primates for dose administration and typically comprise 3— to
`S-French soft rubber pediatric feeding tubes.“1M Tubing is
`measured from the extema] hates to the last rib and marked.
`
`To minimize discomfort, a small amount of xylocaine jelly can
`be placed on the end of the tubing or a drop of 0.5% propar-
`icaine hydrochloride ophthalmic solution is placed directly in
`the hares prior to introducing the tubing into the ventiomedial
`meat-us (Figure 2).
`Except when given in the diet or admixed with food, oral
`administration of substances typically requires some form of
`restraint. In many species, including rodents and nonhuman
`primates, restraint can be the greatest adverse effect of a pro-
`cedure.2573'153 Habituation or positive reinforcement training
`
`Treating laboratory animals—room and factors to consider
`
`to restraint may reduce the stress associated with the proce-
`dural-mm In addition, the administration of large volumes of
`substances by orogastric ornasogastric gavage may cause stress
`due to gastric distension in species that are unable to vomit, such
`as rodents.T1 Therefore, using the smallest volume possible is
`recommended for the oral route of administration, optimally 5
`mL/kg for allspecies [Table I). When rats underwent gavage at
`this volume, no difference was noted betWeen the stress induced
`by gavage compared with that induced by restraint alone.”5
`When large volumes must be administered by gavage, a slower
`delivery rate may be better tolerated by animals
`Limitations of oral dosage may include a slower onset of ac«
`tion compared with parenteral delivery, a potentially significant
`first—pass effect by the liver for those substances metabolized
`through this route with reduced efficacy, lack of absorption of
`substances due to chemical polarity or interference with a bsorp~
`tion by ingesta, poor compliancewith voluntary consumption
`because of poor pa latability or local irritation, lack of systemic
`absorption from the digestive tract, degradation of substances
`by digestive enzymes and acid, and inability to use this route
`in animals that are unconscious or have clinically significant
`diarrhea or eitiesia."l Oral gavage requires moderate technical
`skill and confidence. Research personnel should have training
`and practice prior tostudy initiation to minimize advorse events
`associated with the technique and to ensure that it is performed
`accurately, rapidly, and humanely in experimental animals.
`Intravenous administration. The intravenous route of delivery
`is the most efficient means of delivering substances to animals
`because it bypasses the need for solute absorption. With this
`method, substances are administered as a bolus or infusion
`directly into blood vessels on either an acute or chronic basis
`(Figure 3). Precision electronic infusion pumps equipped with
`alarms to indicate flow interruptions and microdrop infusion
`sets are used to ensure accurate chronic intravenous delivery
`of many substances; however, less expensive precision and
`spring~operated disposable pumps have become available for
`this purpose in recent years and may represent a more economi-
`cal. altemative for experimental intravenous substance delivery,
`depending on the nature of the material to be administered and
`the duration of treatmentg-flm
`Although fluids and parenteral nutrition typically a re infused
`on a continuous basis over several hours or days, the decision
`.to administer- other substances by the intravenous route often
`depends on the pharmacokinetics of the substance, as well as
`the maximum tolerated dose, the time interval over which de-
`livery is required (referred to as dosing intensity), and the need
`to minimize variations in peak and trough blood levels in the
`substance being administered. The actual technique involves
`aseptic preparation of skin for percutaneous venous injection or
`surgical exposure of blood vessels for so bstarl ce administration.
`Intentional intraarterial administration of substances should
`
`be avoided routinely and used only for specific experimental
`conditions, because of the potential for severe complications
`with this route, including blindness, cerebrovascular stroke,
`permanent motor deficits, and limb gat'tg‘renefls'“"5"115‘“fl Sug-
`gested Sims and volumes for intravenous injection and infusion
`of substances are given in Table 1.
`Researchers designing experiments requiring single or
`repeated intravenous treatments should consider technique
`refinements that may enhance animal comfort, including the
`use of the smallest needle or cathetei‘size possible to minimize
`injection trauma, butterfly needles for single injections to mini»
`mize perivascular trauma, 'mdwa-lling catheters and vascular
`access ports for animal comfort and locomotor freedom, topical
`
`601
`
`lnnoPharma Exhibit 1074.0002
`
`

`

`Vol 50. No 5
`journal of the American Association for Laboratory Animal Science
`Seplember 2011
`
`we!W!i"
`
`
`I”.nwill“l—l“
`
`I'---I—fi.‘
`
`
`
`Figure ‘l. (A) Rat voluntarily consuming nutritional supplement from a syringe. Photo courtesy of Colette Wheler. (B) Macaque voluntarily
`drinking medication From a syringe. Photo courtesy of Andrew Winterborn. (C) Pig voluntarily accepting medication when administered in a
`marshmallow. (D) Oral gavage of fish. Photo courtesy of Gerald Johnson.
`
`I
`
`Figu re 2. Chronic nasogastric catheter placement in a rabbit for enteral
`nutrition. Photo courtesy of Colette Wheler.
`
`anesthetic creams and ointments prior to needle placement to
`minimize injection pain, and external pump packs to minimize
`the restriction of animal movement associated with tethering.
`Excellent recent reviews of techniques, equipment, and refine-
`Intraosseous administration of substances, particularly
`ments for using catheters and vascular access ports in animals
`crystalloid fluids, is used in human pediatric medicine and
`have been published.16‘53’39112‘11125'128 A more detailed discussion
`emergency avian and rabbit medicine as an alternative for the
`of dosing equipment for intravenous delivery can be found in
`intravenous route in hypovolemic patients with inaccessible
`the companion article to the current work.131
`
`602
`
`Figure 3. DiFFerent routes oF skin administration of substances. Depict—
`ed are intramuscular (1M), intravenous (1V), subcutaneous (SC), and
`intradermal (1D) routes. illustration courtesy of Gialuii Chiappetta.
`
`InnoPharma Exhibit 1074.0003
`
`

`

`Table ‘i. Recommmded' volumes and sites ofAdrninisti-ation ofsubstanoes to laboratory animals
`
`Treating laboratory annuals—routes and factors to mnsider
`
`Species
`
`Optimal volume [range]
`
`Sitets)
`
`Refereriees
`
`5 mL/ kg (to 20 mL/kg)
`
`Mammals: intragastric
`Fish: esophageal“
`
`21, 82, 134
`127
`
`Route
`Garage
`
`Intravenous
`
`All
`
`Fish
`
`All
`
`Subcutmieous
`
`2 gfkg (gel capsules)
`
`Up to 5 mLfkg (bolus)
`
`Zmszghourly [to imL/kg/h) con-
`inhlsionjc
`
`Rodents: tail or saphenous VEiD
`Rabbits; ear or cephalic Vein
`Larger spades; jugular, cephalic, femtiral, or
`saphenous Vein
`Fish: caudal veinor arteryn‘l’
`
`Mammals.
`
`Maximum of 5 ml.ng per-site
`
`Intraseapular, neck, shoulder, flank
`
`Fish
`
`'1 mL/ kg
`
`Midline and iust anterior to dorsal fm
`
`[nu-adean
`
`Intramuscular
`
`All
`
`All
`
`{LBS-0.1 mLper site
`
`Skin
`
`Maximum of (105 mL/kg per site
`(rodents. rabbits, small nonhuman
`primates, fish)
`
`Mammals: triceps,quadriceps, dorsal lumbar,
`sernimembranosus, Senatendinosus muscles
`
`Fish: base of dorsal fin or between dorsal [in
`and lateral line-
`
`Epidural
`
`lntraperiteneal
`
`Intranasal
`
`Mammals
`
`0.15—0.51 mIJkg‘7i (6 ml. total volume
`in patients up to .35 kg}
`
`All
`
`Maximum of 10 mL/kg
`
`See text
`
`Render-1m
`
`Minimum of 35¢. per arlimalé
`(50 pLj
`
`16
`
`82
`
`l6
`8'2, 89
`
`82
`
`53
`
`52
`
`82
`
`16
`
`47,. 7’3, 138
`
`82
`
`82,. 1'21
`
`200 to 500 pL-per animal
`
`Dog. cats, nunhmnan
`primates, rabbits
`The physieochemical properties of the substance to be administered will markedly affect the volumes that are tolerated. For example. lower
`volumes than those listed in this table may need to be used for highly viscous or irritating substances.
`'Sedation or light anesthesia may be needed for larger species.
`I‘Renal first-pass effect is possible when injecting by using this route.
`rRates unwiderably lower than 2 mL/lrg hourly may result in catheter patency‘ issues in rodents.
`“Larger volumes may result in more rostral spinal effects. Intratl'lttal iniection volumes and doses are typically 50% of those used For epidural
`delivery.
`“In mice, volumes less than 35 11L have been reported to be distributed primarily to the upper respiratory tract, whereasa SO-uL volume was
`predominantly deposited in thelower respiratory tract.
`
`82
`
`603
`
`lnnoPharma Exhibit 10740004
`
`

`

`Vol 50, No 5
`Journal of the American Association for Laboratory Animal Science
`September 2011
`
`or collapsed virginsfi'l'fi‘“29 The medullary cavity contains non-
`collapsing venous sinuses that directly enter into the central
`venous circulation and substances administered mtraosseously
`are generally detectable im mediame after administration. The
`technique is difficult to perform without advanced training and
`is potentially invasive, with considerable risk for postptocedural
`ostecmyelitis, fat embolirzation, iatrogenic fracture and growth
`plate injury, and pain. lnttaosseous administration typically is
`conducted in fully anesthetized animals.
`Substances administered intravenously or intraosseously
`must be delivered aseptically and should be sterile; free of
`particulates that may induce foreign body emboli; and mini-
`mally irritating to vascular endothelia, to prevent vasculitis
`and thrombosis, and to erythrocytes, to minimize lysis. Cerv
`tain oily substances, such as cremaphor, and various alcohols,
`surfa ctants, and other vehicles and excipients may induce
`hemolysis when introduced intravenously; these substances
`should be avoided, whenever possible, or first evaluated in
`vitro for safety/1‘15""!act The intravenous route of substance de-
`livery, although efficien t, can be risky in animals, and persons
`conducting this technique require training and practice to ensure
`competency. Careful control of hemostasis must be instituted.
`when the catheter or needle is removed, to minimize blood loss
`and painful hematoma formation. When fluids or infusions are
`ad ministered chronically, anima ls should be monitored closely
`for signs of fluid overload and pulmonary edema, such as
`dyspnea and cyanosis.” Chronically implanted catheters and
`vascular access ports require regular cleaning and maintenance
`to ensure patency and prevent infection.
`Administration to skin and muscle. Some substances can
`
`'be administered directly to the skin surface (epicutaneous
`administration} for a topical affect. The extent of absorption
`of materials through the skin and into the systemic circulation
`(that is, percutaneous or transdermal delivery} depends on: the
`surface area over which the substance is applied; the concentra-
`tion of the substance administered; the lipid solubility of the
`material or vehicle; whether the skin surface is intact; the skin
`thickness at the site of application: the length of time that the
`material is in contact with the skin surface; and the degree of
`skin hydration and surface Occlusion, in that covered and well»
`hydrated skin absorbs substances faster than does uncovered or
`dryskin.” For fish, specialized chambers can be constructed to
`expose the skin or gills specifically to testsubstancer-..1'5-53 When
`administrating substances topically to the skin of mammals,
`overlying hair is clipped to minimize matting and maximize
`contact with the material to be applied, and the skin surface is
`cleaned prior to application. Absorption of substances across
`the epidermis occurs through paracellular and transcellular
`mechanisms into the stratum corneum, to the stratum spinosum,
`and then to the basal layers of'ihe skin and late1; the dermis, as
`Well as into the subcutaneous space through hair follicles and
`accessory glarldsffl33
`Caution must be exacised to avoid applying caustic or irritat-
`ing material directly onto the skin, and some substances may
`induce local sensitization reactions. Consideration should be
`
`givento the potential for systemic toxicity when administei'ing
`substances topically, particularly if the site is readily accessible-
`for gmoming.“ Application of thin layers of cream or ointment
`to the skin at more frequent intervals may be more efficacious
`with less potential for systemic toxicity than is less frequent
`application of thicker layers.
`Transdermal or percutaneous delivery represents a similar
`route of administration except that materials are applied to
`the skin surface deliberately, usually by means of a patch, for
`
`604
`
`absorption across the epithelial barrier into the systemic circula-
`tion. Typically, this method produces very constant blood levels
`of the-substance being administered. Percutaneous delivery is
`an attractive alternative to other parenteral routes, avoiding the
`need for repeated animal restraint, painful injections, and sharps
`hazards. In addition, materials can readily be removed from the
`skin surface if dosing needs to be interrupted orif adverse effects
`are noted. Transdermal delivery of substanCes may be acute or
`chronic, and current techniques for delivering substances by this
`route have been reviewed recentlyms-w" The skin is prepared as
`for topical delivery. When a transdermal delivery system will
`be used, the agent and delivery system (for example, patch)
`must be applied in advance of when the desired effect needs
`to occur; based on the pharmacokinetics of substance absorp»
`tion. The product should be applied in such a way to protect
`it from ingestion and contamination, and the signs of toxicity
`after inadvertent ingestion by the animal should be known.
`Commercially available human transdermal products can be
`difficult to use in animals because of the much larger doses of
`substances impregnated into products intended for adult hu~
`man use. Cutting transdermal patches to scale-down the dose
`being administered is not recommended; however, covering
`a portion of the patch to limit substance administration may
`be- used. Animals should be observed closely for toxicity, and
`as for topical delivery methods, skin sensitization may occur
`over time with transdermal product use.“ Animals must be
`prevented from removing and ingesting patches.
`Nonirritating substances may be given subcutaneously,
`which represents a rapid, inexpensive, and simple method of
`parenteral substance administration (Figure 3). Substances ad»
`ministered subcutaneously often are absorbed at a slowar rate
`compared with other parenteral routes, providing a sustained
`effect. The exact mechanism of absorption is unknown but is
`thought to be due to uptake of macromolecules within the
`subcutis by small capillaries underling the skin, with minimal
`lymphatic absorption.“ Substances deliVered subcutaneously
`can be aqueous or oily fluids, depots ofcily materials for slow
`absorption, so lid pellets, or injected into suitably sized osmotic
`minipumps or other implantable pumps, which subsequently
`are surgically inserted into a subcutaneous pocket. Because
`the subcutaneous space is largely a virtual space, it. can be an
`excellent site for large volume fluid delivery in small or dehy«
`drated animals, avoiding technical difficulties and problems
`sometimes seen with direct intravenous administration, such as
`fluid overload and pulmonary edema, because excess subcuta-
`neous fluid is excreted rapidly by the kidneys. Compared with
`intravenous delivery, the subcutaneous route is a simple one to
`mastei'; however, training and competency of personnel should
`be monitored to ensure that substances are deliveled accurately
`and that inadvertent intravenous injection is avoided. Careful
`consideration should be-given to using an appropriately sized
`needle, and humane and aseptic periinjection techniques. The
`skin overlying the site selected for injection should be loose
`to minimize discomfort, and the needle should be inserted at
`a shallow angle to minimize damage to underlying tissues.
`Passing a small—gauge needle through a thick rubber stopper
`to fill an attached syringe prior to injection may dull the needle
`point, enhancing injection discomfort. Contaminated substances
`injected subcutaneously typically will result 'm abscess forma-
`tion. Recommended volumes and locations for subcutaneous
`
`injections are presented in Table 1, madvertent subcutaneous
`administration is‘a common complication of intradermal'injec~
`tions, and small, sharp needles are required for success with
`intradermal delivery}:
`
`lnnoPharma Exhibit 1074,0005
`
`

`

`lntra muscular administration of substances is a common
`
`parenteral route in large animals and humans but often is
`avoided in smaller species because of the reduced muscle mass.
`Generally, intramuscu la r injections result in uniform a nd rapid
`absorption of substances, because of the rich vascular supply
`(Figure 3). Smaller volumes are administered intram uscular'ly
`than for subcutaneous delivery (Table l}. The intramuscular
`technique requires more skill than does subcutaneous injec—
`tion and should be conducted only by well-trained personnel.
`Intramuscular injection of irritating substances or inadvertent
`injection of nerves may result in paresis, paralysis, muscle
`necrosis, and localized muscle sloughing. “B Repeated injec—
`tions may result in muscle inflammation and necrosis-10 Other
`considerations and cautions for using the intramuscular route
`for substance delivery are similar to the subcutaneous route.
`Epidural and intrathecai administration. For rapid effects of
`substances on cerebrospinal tissues or meninges, substances can
`be administered into the epidural or suba ra chn oid {in tra theca I}
`space of the spinal cord (Figure 4, Table 1}. This technique avoids
`absorptive problems otherwise presented by the blood—brain
`barrier, The route is used commonly to induce spinal anesthesia
`or to introduce contrast media for visualizing vertebral bodies or
`the spinal cord of large animal species. The technique requires
`animals to be sedated heavily and given a local anesthetic block
`over the spinal needle insertion site; alternatively animals can
`undergo general anesthesia prior to implementation 3133 Asep—
`tic preparation of the skin overlying the injection site and use
`of sterile technique for needle insertion are critical for success
`and animal recovery. The exact location of needle insertion and
`volume of injectate will vary between species and for intrathe—
`cal compa red with epid oral administration, and several factors
`con tribute to procedural success {see reference 138 for review}.
`Epidural fat, lipophilicity of the. substance being administered,
`leakage of injectate through intervertebral spaces, and pro—
`nounced meningovertebral ligaments all will limit or alter the
`spread of material being introduced by epidural or intrathecal
`routesfifi This limitation may be problematic, in that increased
`quantities of substances may need to be administered for effect,
`with the possibility ofspill-over into systemic circulation, result-
`ing in adverse effects, such as profound respiratory depression
`requiring prolonged ventilation. Visualization of cerebrospinal
`fluid after spinal needle insertion confirms intrathecal placement
`of the needle. If this fluid is noted when attempting an epidural
`injection, the needle should be withdrawn and repositioned,
`or the dose of the substance administered should be reduced,
`beca Use the kinetics of substance absorption from epidural
`compared with intrathecal delivery can be markedly different.13ml
`Intra thecal or epidural administration of substa nces requires
`considerable technical skill and in-depth knowledge of anesthe-
`sia, analgesia, and spinal cord and vertebral column anatomy.
`These techniques should be performed only by well-trained
`personnel. AdVerse even ts associated with epidural administra—
`tion of substances to small animals include prolonged time for
`hair regrowth over the injection site, pruritus, urinary reten—
`tion, nausea, vomiting, and prolonged and severe respiratory
`depression.”2
`lmraperitonea! administration. injection of substances into the
`peritoneal cavity is a common technique in laboratory rodents
`but rarely is used in larger mammals and humans. lntraperito-
`neal injection is used for small species for whid‘l intravenous
`access is challenging and it can be used to administer large vol-
`umes of fluid safely (Table l;- or as a repository site for surgical
`implantation of a preloaded osmotic minipump. Absorption of
`material delivered intraperitoneally is typically much sloWer
`
`Treating laboratory anirnalsuroutes and factors to conra'der
`
`Subcutaneous Fat
`
`Supraspinous Ligament
`
`
`
`Interspinous Ligament
`
`Ligamentum Flavum
`
`
`Figure 4. Epidural (ED) compared with intralhecal [IT] injections in
`die distal lumbar spine Illustration courtesy of Gianni Chiappetta.
`
`than for intravenous injection. Although intraperitonea] de-
`livery is considered a parenteral route of administration, the
`pharnracokinetics of substances administered intraperitonea lly
`are more similar to those seen after oral administration, beca use
`the primary route of absorption is into the mesenteric vessels,
`which drain into the portal vein and pass through the liver?”l
`Therefore substances administered in traperitoneally may
`undergo hepatic metabolism before reaching the systemic cir—
`culation. In addition, a small amount of intraperitonoal injectate
`may pass directly across the diaphragm through small lacunae
`and into the thoracic 1y mph .3
`In mammals, intraperitoneal administration typically is
`conducted in conscious animals by using firm manual restraint,
`with the head and body tipped downward to move viscera away
`from the surface of the ventral abdomen. Injections in rodents
`are made in the lower right abdominal quadrant away from the
`midline to avoid inadvertent injection into the urinary bladder
`or cecumfii‘ The syringe plunger may be withdrawn prior to
`injection, specifically looking for urine, blood, or digesta in the
`needle hub; if these fluids are seen, the needle should be with«
`drawn, replaced, and repositioned prior to injection. The most
`common mistake is to puncture the skin at too acute an angle,
`resulting in subcutaneous rather than intra peritoneal admin-
`istration. For intraperitoneal injections in fish, the animals are
`restrained on their side on a flat surface, and the needle should
`enter along the midline, just anterior to the pelvic fin s. Larger
`fish may require sedation or light anesthesia for appropriate
`restraint“?
`
`Materials injected intraperitonea lly should be sterile, isotonic,
`and nonirritating. Irritating substances injected intraperito—
`neally ma y induce painful ileus and peritonitis in rodents, with
`subsequent adhesions .43 Th is drawback is typified by the effects
`of undiluted chloral hydrate when administered intraperito-
`neally in rats-7“" injections of identical doses of chloral hydrate
`in less concentrated solutions may avoid peritoneal irritation,l:‘7
`and this technique may be Used for other potentially irritating
`substances. Although technically a simple procedure to perform,
`training and competency of personnel should be monitored to
`ensure that substances are delivered accurately and that inad-
`Vertent intracecal or in tracystic injections are avoided.
`intranasal, intratracheai, and inhalationar' administration. in
`research settings, animals generally are sedated or anesthe—
`tized” for the intranasal and intratracheal routes of delivery,
`to minimize struggling and sneezing. Volumes administered
`intranasally are. small compared with those of other routes (Ta-
`605
`
`InnoPharma Exhib