Drug Administration and Antibiotics for Exotics

What considerations must we have for small mammals when administering drugs?

High metabolic rate, small muscle mass (dosage), site of administration, take into account microflora of gut (don’t disrupt)

What considerations must we have for birds when administering drugs?

High metabolic rate, hide signs of illness, renal/hepatic portal system (don't put in caudal limbs & consider site of administration)

What considerations must we have for reptiles when administering drugs?

Exothermic (metabolism dependent on temperature), renal portal system and difficult to assess pain.

How are drugs adminstered enterally in exotics?

Mixed with food or fluid and fed by syringe or tube.

(be aware of bioavailability i.e. pharmacokinetics of drug)

Give at least 2 advantages of enteral administration in exotics

• Economical

• Can be administered by owner

• Relatively safe

Give at least 2 disadvantages of enteral administration in exotics

• Possibility of aspiration

• Lack of palatability (won't consume voluntarily)

• Slower onset of action (through digestive tract first, absorption rate slower)

• First pass metabolism by liver can = reduced efficacy

• Variable absorption

Describe enteral drug administration in birds

Practical if crop tubing —> inadvisable in drinking water/food —> unable to monitor dosage (sick birds unlikely to be eating/drinking properly), can make food or water taste strange/bitter, bioavailability considerations

Describe enteral drug administration in reptiles. What needs to be considered?

• Challenging —> best by feeding tube

• Be aware of GI shutdown between meals i.e. avoid in fasting reptiles

• Consider POTZ —> temperature affects absorption, distribution, metabolism & excretion of drug

• Hepatic portal system —> orally administered drugs often ineffective

Give at least 2 advantages of parenteral administration in exotics

• Can use for drugs which are poorly absorbed orally (i.e. if GI system dysfunctional)

• Can give immediate onset of action (IV)

• Can give delayed onset of action (IM/SC)

Give at least 2 disadvantages of parenteral administration in exotics

• Can be painful

• Can be tricky in small patients (volumes etc.)

• Peculiarities in reptiles/birds —> location of injection site must be carefully considered

Give at least 2 main parenteral administration strategies available for exotics

• SC

• IM

• IV

• IP

• IO

What areas of a small mammal are appropriate for SC injection? Why?

Flanks, scruff (dorsal shoulder).

Need to allow for volume expansion

What are the considerations for SC injections in ferrets & guinea pigs?

Ferrets —> tough skin in scruff i.e. can be difficult to inject

Guinea pigs —> dorsal fat pad runs just behind ears so injecting in scruff can be painful

What gauge of needle should be used for rodents?

25-27g

What gauge of needle should be used for rabbits?

23-27g

What gauge needle should be used in ferrets?

25g (in most)

What gauge should be used in birds for SC?

Small birds = 27/27g
Others = 23/25g

How to SC inject in birds?

Use inguinal fold on inner thigh, half-way between body and stifle, or axillary region, or intrascapular (scruff!) region – for this stay close to elbows to avoid injection into the cervical air sac.

What is a consideration when SC injecting in reptiles?

Drug uptake can be slow/unreliable —> can be useful for administration of small volumes of fluid

How to SC inject in reptiles?

• Snakes/Lizards – insert needle between scales on lateral aspect of body, no need to tent skin.

• Chelonians – use ventral neck fold, or inguinal skin fold

• Ensure needle inserted to reasonable depth (about half its length) to reduce seepage from injection site – SQ space less expansive.

What areas of a small mammal are appropriate for IM injection?

• Paralumbar (rabbits, chinchillas and guinea pigs)

• Quadriceps (ferrets rabbits and small rodents)

Where to IM inject in birds?

• Pectorals, ideally close to keel bone i.e. muscle thickest here

• Thighs (remember renal/hepatic portal systems)

What is the preferred route of administration in reptiles? Describe why

IM —> upper arm in chelonians & lizards, epaxial muscles in snakes

Avoid caudal half of body due to first pass effect of renal portal system/hepatic portal system

What areas of a small mammal are appropriate for IV injection?

• Cephalic and lateral saphenous in ferrets and rabbits only.

• Marginal ear vein in rabbits but risk of skin sloughing
  (not practical for other small mammals)

• Tail veins in lab animals

What area do we IV inject in birds?

Right jugular vein —> bigger than left

Basilic vein

Medial metatarasal

What area do we IV inject in reptiles?

Right jugular in chelonians —> bigger than left

Tail vein in lizards & snakes

Which route is used in small animals vs reptiles (intraperitoneal vs intraceolomic)?

Intraperitoneal in small mammals

Intraceolomic in reptiles

What are the advantages of intraperitoneal administration in exotics?

Large absorptive surface (can put a lot of drug in there).

What are the disadvantages of intraperitoneal administration in exotics?

• Variable and unpredictable uptake

• Risks damage to organs and injection into organs

What is safe positioning for IP injection into rodents?

Low (caudal) right quadrant).

What is safe positioning for IP injection in rabbits?

Lower (caudal) left quadrant (with extreme caution due to large abdominal organs)

Why caution when intracoelomic injecting reptiles?

Lack of functional diaphragm

Where to intracoelomic inject reptiles?

Lizards = right caudal quadrant

Snakes = caudal third of coelom, cranial to cloaca

Chelonia = prefemoral fossa (just in front of rear limb)

How is intraosseus administration performed in small mammals?

• Via catheter

• Into greater trochanter of femur, proximal humerus or proximal tibia

How is intraosseus administration performed in birds?

Distal ulna or proximal tibia, avoid humerus/femur due to pneumatisation

How is intraosseous injections in reptiles administered?

Proximal tibia

(limited to lizards & chelonia)

What is required first before IO administration?

Heavy sedation or anaesthesia.

What consideration must we have when using antibiotics in small mammals?

Herbivorous species have important resident microbial populations important for gut health

Give at least 2 classes of antibiotics that we can use in small mammals

Medications for treating small mammals:

Metronidazole, Fluoroquinolones, Tetracyclines, Sulphonamides, Macrolides (except erythromycin!)

Aminoglycosides(??)

Give at least 2 antibiotics to avoid when treating small mammals

PLACE; Penicillins, Lincosamides, Aminoglycosides, Cephalosporins, Erythromycin

Give at least 2 antibiotics licensed for rabbits

• Trimethoprim-sulphamethoxazole

• Enrofloxacin

• Fucidic acid

• Gentamicin

Are there licensed antibiotics for ferrets?

No!

What antibiotics are commonly used for birds?

• Fluoroquinolones

• Penicillins/Cephalosporins

• Aminoglycosides

Describe fluoroquinolone use in birds

-IM can cause necrosis

-Oral administration safe but tastes bitter

-Generally well tolerated

Describe penicillin/cephalosporin use in birds

High therapeutic index so safe

Need to give frequently due to high metabolic rate of birds

Describe aminoglycoside use in birds

Can be toxic so care with dehydrated patients

What antiotics are licensed for birds?

Enroflaxacin (baytril)

Give at least 2 antibiotics we can use for reptiles,

• Cephalosporins

• Fluoroquinalones

• Sulphonamides

• Metronidazole

• Aminoglycosides

• Some penicillins

What are the licensed antibiotics for reptiles?

Trimethoprim-sulphamethoxazole and enrofloxacin (Baytril).