Medication in reptiles
Reptile owners are routinely instructed on oral or intramuscular (IM) drug administration techniques for outpatient care. In many instances and in many species, parenteral injections are preferred over the oral route. Injectable medications can be delivered IM, subcutaneously (SQ), intracoelomically (IC), intravenously (IV), or intraosseously (IO). Before beginning drug administration, ensure the patient is well hydrated and maintained at its preferred optimum temperature zone.
Intramuscular route: Video
Intramuscular injections are the most common parenteral route for drug administration in reptiles.
Video narrated and produced by M. Scott Echols, DVM, DABVP (Avian Practice)
Historically the tail and rear limbs have been avoided because of the presence of a renal portal system. Research has shown that a first pass effect may not occur as previously assumed (Beck 1995, Holz 1997, Holz 2002). Nevertheless we still do not know if injections in the caudal half of the body are appropriate with all medications or in all (or even most) species. Therefore most clinicians still inject medications into the cranial half of the body (Fig. 1).
Specific sites for IM injection will vary (Box 1). In lizards, injections are made into the most muscular part of the upper arm or forearm. Take care to avoid the cranial surface of the limb to minimize the risk of radial nerve damage (Fig. 2). The forelimbs are also used in chelonians (Fig. 3). The only muscle group available for intramuscular injection in snakes is the epaxial musculature (Fig 4).
|Box 1. Intramuscular injection sites in reptiles|
|Chelonian||Upper arm (deltoid or triceps), forearm (biceps)|
|Snake||Epaxials in cranial half of body|
Whenever possible, avoid IM injections in small species like geckos. When injecting medication into the forelimb, avoid the cranial surface to minimize the risk of radial nerve damage.
Insert the needle between scales in squamates (lizards and snakes). After inserting the needle, apply negative pressure as you would in any animal to prevent inadvertent injection into a blood vessel. If multiple injections are required, be sure to alternate sites to minimize inflammation and improve patient compliance.
The medication prescribed will vary with the species, the clinical problem, culture results (if using antibiotics), and the planned duration of treatment, however keep in mind that the manufacturer recommends enrofloxacin (Baytril®, Bayer Animal Health) be administered via injection only once due to its alkaline pH. Repeated IM injections of enrofloxacin can cause muscle necrosis. This necrosis is typically only recognized at necropsy but is undoubtedly painful. In rare cases, repeated injections can also lead to skin depigmentation and sloughing (Fig. 5) (Mitchell 2006).
Home care instructions
Instruct owners to alternate injection sites (as described above) and to return needles for proper disposal.
Reptiles have a relatively small subcutaneous space with limited vascularity making absorption of fluids or medication variable (Mitchell 2006). There is no need to tent the skin in reptiles (Box 2). Insert the needle parallel to the body wall in between the scales. Advance more than half of the needle’s length to reduce the risk of fluid leakage.
|Box 2. Subcutaneous injection sites in reptiles|
|Chelonian||Axillary and inguinal space|
|Lizard||Lateral body wall, inguinal space|
|Snake||Lateral body wall|
Some turtles also have a thin strip of skin at the junction of the plastron (or lower shell) and bridge (or where the upper and lower shells connect). This area may be used for injection of small volumes even when the chelonian is withdrawn into its shell (Sykes 2006).
The intracoelomic route is a not a common site for administration of medications.
- Position squamates in dorsal recumbency and chelonians in lateral recumbency.
- Clean the area with alcohol or another topical disinfectant.
- To prevent injection of fluids or drugs into the lungs and air sacs, insert the needle into the caudal third of the coelom in chelonians and lizards or the caudal one-fourth in snakes. Avoid the ventral midline in lizards to prevent laceration of the ventral abdominal vein.
- Insert the needle at the junction between the lateral scales and ventral belly scutes in snakes. In chelonians, insert the needle where skin folds attach to the bridge.
- Advance the needle parallel to the body wall.
- Always aspirate the needle before injecting to make sure the needle did not enter the respiratory tract.
Intraosseous (IO) injections are typically used for fluid administration in reptiles, however anything that may be injected intravenously may also be injected IO. Intraosseous catheter use is typically limited to lizards. The proximal tibia is typically used, however the distal femur is an alternate site.
Intravenous injections are the preferred route for drug administration in the septic reptile (Mitchell 2006). Intravenous catheters often require cut down, however only sites that do not require a surgical incision are listed below (Box 3).
|Box 3. Intravenous injection sites in reptiles|
|Chelonian||Right jugular vein|
|Lizard||Tail vein, ventral abdominal vein|
Oral drug administration can be challenging in reptiles due to the sharp teeth of some species like large monitors and the difficulty in opening the chelonian mouth. Research also suggests the reptile gastrointestinal tract may be quiescent between meals, making oral drug administration of dubious value in a large, fasting reptile.
Among reptiles, oral drug delivery is most frequently used in lizards. One “easy” method is to hide medication in food items. Inject drug into prey items such as a mouse or mealworm, or place fruit-flavored medication on top of herbivore diets. Limit the amount fed to ensure the full dose is consumed, and monitor food intake carefully.
Oral medications may also be delivered by syringe or tube. Some lizards may simply lick at flavored compounded medications offered via syringe. A feeding tube may also be passed as described below:
- Something to create a gap in the oral cavity so that the speculum and/or tube may be introduced: plastic card (i.e. credit card) or exposed x-ray film. A cotton-tipped applicator and some speculums (see below) will also serve to open the mouth in snakes.
- Mouth speculum: rubber spatula, rubber coated infant spoon, hemostat of appropriate size padded with tape or elastic bandage material, metal avian speculum, small nylon bone, plastic-coated paper clip, syringe case with the closed end removed, tape roll
- Water-soluble lubricant
- Metal ball-tipped gavage tube or rubber feeding tube
- Pre-measure the tube from the mouth to the reptile’s midpoint, the approximate location of the stomach.
- Lubricate the tube with the water-soluble lubricant or water.
- Open the mouth, taking care not to injure the teeth or beak.
Option 1) To manually open the mouth in some lizards and snakes, hold the lower jaw with your fingers and apply steady downward pressure.
Option 2) In some lizards, such as iguanas or bearded dragons (Pogona vitticeps), gently pulling down on the dewlap can also open the mouth (Fig. 6). Perform this maneuver gently because excess force can damage the hyoid apparatus, and even permanently curve the lower lip in patients with metabolic bone disease (Sykes 2006).
Option 3) Use a plastic card (or similar item) and speculum to open the mouth as needed.
Caution: Despite the evident strength of many turtles or tortoises, use careful technique as opposed to brute strength to open the mouth. Aggressive manipulation can injure the cervical spine or the cutting edges (or tomia) of the beak. If frequent tubings are indicated in chelonians, place an esophagostomy tube instead.
- Identify the glottis at the base of tongue.
- Bypass the glottis, gently passing the tube into the stomach.
The cloaca allows extensive resorption of fluids and other materials, and cloacal administration of some medications like fenbendazole has been described in chelonians (Innis 1995). Unfortunately this same physiology can create a dangerous osmotic gradient to occur with the use of soap or dioctyl sodium sulfosuccinate so avoid these products in reptiles (Sykes 2006).