Selamectin (Revolution)

Selamectin, marketed under the brand name Revolution, is a macrocyclic lactone antiparasitic medication that has become a popular and effective treatment option for mite and lice infestations in guinea pigs. This topical medication offers the significant advantage of convenient at-home application, eliminating the need for veterinary visits for injectable treatments while maintaining excellent efficacy against common guinea pig ectoparasites. Selamectin is widely recognized in exotic animal medicine as a safe and effective treatment for sarcoptic mange caused by Trixacarus caviae, fur mites, and lice species that affect guinea pigs. The medication's development specifically for companion animal use and its extensive safety testing in small mammals have contributed to its acceptance as a first-line treatment option alongside injectable ivermectin.

The mechanism of action of selamectin involves binding to glutamate-gated chloride channels in the nervous system of invertebrate parasites, causing increased chloride ion permeability that leads to paralysis and death of the parasite. This mechanism is shared with other macrocyclic lactones including ivermectin and moxidectin, providing reliable activity against a broad spectrum of ectoparasites. Following topical application, selamectin is absorbed through the skin and distributed throughout the body tissues, achieving systemic concentrations that expose parasites to the drug whether they reside on the skin surface or within burrows in the epidermis. The drug maintains effective antiparasitic concentrations for approximately one month, making monthly application sufficient for many treatment and prevention protocols.

Selamectin is available as a topical spot-on solution in various package sizes intended for cats and dogs of different weights. For guinea pig use, the smallest available concentration is typically employed, with specific dosing determined by the prescribing veterinarian based on the guinea pig's body weight. The medication is applied directly to the skin, usually between the shoulder blades where the guinea pig cannot groom it off, and is absorbed over the following hours to days. The convenient application method makes selamectin particularly suitable for guinea pig owners who may be apprehensive about injectable medications or who prefer the simplicity of at-home treatment. Treatment protocols for mite infestations typically involve application at two to four week intervals for two to four treatments to address all parasite life stages.

The safety profile of selamectin in guinea pigs is well-established through clinical experience and research, with the medication demonstrating a wide margin of safety when used at appropriate doses. Selamectin was specifically developed and tested for use in companion animals, with safety studies including application to small mammals. Side effects are uncommon and typically mild when they occur. As with any medication, proper veterinary guidance ensures appropriate diagnosis, correct dosing based on accurate body weight, and development of a treatment protocol suited to the individual patient's condition. Working with an exotic veterinarian experienced in guinea pig medicine provides the foundation for safe and effective selamectin therapy.

The primary indication for selamectin use in guinea pigs is the treatment of ectoparasitic infestations, with sarcoptic mange caused by the burrowing mite Trixacarus caviae being the most significant condition addressed by this medication. Sarcoptic mange causes severe pruritus, hair loss, skin thickening, and substantial suffering in affected guinea pigs, and selamectin provides highly effective treatment that typically resolves the infestation with appropriate repeat applications. The medication's systemic distribution after topical absorption ensures that drug reaches mites in their burrows within the skin, where burrowing parasites live and reproduce. Response to treatment is typically excellent, with resolution of pruritus beginning within days and complete elimination of the infestation achieved with full treatment compliance.

Examining the primary use more thoroughly, selamectin's effectiveness against sarcoptic mange reflects its ability to achieve therapeutic tissue concentrations through transdermal absorption and maintain these levels for approximately one month after each application. Guinea pigs suffering from severe mange present with intense scratching, significant hair loss often starting on the head and spreading across the body, scaly or crusty skin lesions, and obvious distress that affects eating, activity, and quality of life. The expected response to selamectin treatment includes progressive reduction in itching within the first week, gradual improvement in skin condition, and hair regrowth over subsequent weeks as the infestation resolves. Guinea pigs from pet stores, breeders, rescues, and shelters where animal-to-animal transmission is more likely are most commonly affected, though any guinea pig can become infested.

Secondary uses for selamectin in guinea pig medicine include treatment of fur mites including Chirodiscoides caviae, which cause less severe but still troublesome skin irritation and hair loss, and lice species including Gliricola porcelli and Gyropus ovalis. These surface-dwelling parasites cause discomfort that warrants treatment even though symptoms are typically less dramatic than sarcoptic mange. Selamectin's systemic distribution exposes surface parasites to effective drug concentrations. The medication is also sometimes used prophylactically when introducing new guinea pigs to existing colonies, though this practice varies among veterinarians. Prevention of flea infestation is another labeled use of selamectin in dogs and cats that extends to guinea pig applications in flea-endemic environments.

Additional clinical applications of selamectin in guinea pigs may include treatment of certain ear mites and prevention of environmental flea exposure in households with dogs or cats. While guinea pigs are not primary hosts for common cat and dog fleas, they can be bitten by fleas in infested environments, and selamectin provides protection. Some exotic veterinarians include selamectin in regular wellness protocols for guinea pigs in multi-pet households where parasite prevention is part of routine care. The convenient monthly application schedule aligns with other preventive care activities, facilitating owner compliance with treatment recommendations.

Selection criteria for choosing selamectin over other antiparasitics in guinea pig practice include the convenience of topical application that owners can perform at home, the product's development and safety testing specifically for companion animal use, the extended duration of action requiring only monthly application, and owner preference for non-injectable treatment options. Advantages of selamectin include elimination of veterinary visits for each treatment, reduced handling stress for guinea pigs who find clinic visits stressful, and the established safety profile in small mammals. Patient factors influencing selection include the severity of infestation, owner comfort with topical medication application, and any previous experience with different antiparasitic treatments.

The dosing protocol for selamectin in guinea pig patients requires veterinary determination of the appropriate product selection and dose based on accurate body weight measurement. Revolution products are available in various sizes intended for different weight ranges of cats and dogs, and the veterinarian selects the appropriate product and amount for guinea pig use based on published guidelines and clinical experience. Accurate weighing using a gram scale is essential, as guinea pig weights can vary considerably and proper dosing depends on knowing the actual current body weight. Individual patient factors including age, health status, coat type, and severity of infestation may influence the specific treatment approach. The exotic veterinarian's guidance ensures appropriate product selection, dosing, and treatment scheduling.

Typical dosing guidelines for selamectin in guinea pigs generally recommend approximately six to eighteen milligrams per kilogram of body weight applied topically, though specific amounts depend on the product concentration used and veterinary protocols. The kitten-sized Revolution product is commonly employed for guinea pigs, with the veterinarian specifying the portion of a tube appropriate for the individual guinea pig's weight. Application is typically performed monthly for treatment of active infestations, with most protocols calling for two to four monthly applications to address all parasite life stages as eggs hatch and become susceptible to the drug. Some veterinarians prefer biweekly application during active treatment, extending to monthly intervals for prevention after infestation resolution. Maximum dose considerations emphasize staying within established safe ranges.

Treatment duration for mite infestations using selamectin typically spans two to four months, with monthly applications addressing successive generations of parasites as eggs present at initial treatment hatch and become susceptible to the medication. The treatment period must be long enough to break the parasite life cycle completely, eliminating all stages before reproduction can reestablish the infestation. Factors affecting treatment length include severity of the initial infestation, whether all in-contact guinea pigs receive simultaneous treatment, thoroughness of environmental cleaning, and the individual patient's response to therapy. Follow-up veterinary evaluation confirms resolution through improvement in clinical signs and potentially skin scraping examination to verify absence of mites.

Administration instructions for selamectin emphasize proper technique to ensure skin contact and maximize absorption. The guinea pig should be gently restrained, and the fur should be parted between the shoulder blades to expose the skin. The measured amount of selamectin solution is applied directly to the exposed skin, not to the fur. This location is chosen because guinea pigs cannot groom this area, preventing ingestion of the medication. The solution should be allowed to dry before handling the guinea pig extensively or returning it to contact with cage mates. Application should not be performed immediately after bathing, as wet skin or fur may affect absorption. Timing relative to feeding is not critical, but calm handling minimizes stress for the guinea pig during the application process.

If a scheduled selamectin application is missed, the owner should contact their veterinarian for guidance. Generally, a missed dose should be applied as soon as remembered, with subsequent doses scheduled at the usual monthly interval from the late application. Doubling the amount applied to make up for a missed dose should never be done, as this increases the risk of adverse effects. Because selamectin has an extended duration of action, modest delays in application may have less impact on overall treatment success than with shorter-acting medications, but maintaining the treatment schedule as closely as possible optimizes outcomes. Documentation of actual application dates helps track treatment progress.

Completing the full course of selamectin treatment as prescribed by the veterinarian is essential for achieving complete resolution of parasitic infestations. The rationale for multiple applications relates to the drug's inability to kill eggs, requiring that subsequent generations hatch and be exposed to medication before they can mature and reproduce. Stopping treatment prematurely because the guinea pig appears improved may leave residual parasites that reestablish the infestation, necessitating additional treatment and prolonging the overall course. If adverse effects occur during treatment, owners should contact their veterinarian for guidance. Maintaining optimal guinea pig health through proper nutrition including daily vitamin C supplementation, clean housing, and stress reduction throughout the treatment period supports recovery from both the parasitic infestation and any medication effects.

The general tolerability of selamectin in guinea pigs is excellent, with the medication demonstrating a wide margin of safety when used at appropriate doses. Most guinea pigs treated with properly applied selamectin experience no noticeable adverse effects and tolerate the medication very well. This favorable safety profile, combined with convenience of application and proven efficacy, explains selamectin's popularity as a guinea pig antiparasitic treatment. Owners should nevertheless remain aware of potential adverse effects and monitor their guinea pig following each application, as individual variation means some animals may be more sensitive than others. The development of selamectin specifically for companion animal use included extensive safety testing that supports its use in small mammals.

Common and mild side effects of selamectin in guinea pigs are infrequent but may include temporary skin reaction at the application site, which can manifest as mild redness, flakiness, or temporary hair loss at the spot where the medication was applied. Some guinea pigs may show transient lethargy or decreased activity for twelve to twenty-four hours following application. Mild gastrointestinal effects are uncommon with topical selamectin but might include slightly softer stool or minor temporary appetite reduction. These mild effects, when they occur, typically resolve spontaneously within one to two days without intervention. Monitoring food and water intake and fecal output helps identify any effects early and distinguish normal variation from concerning changes.

Moderate side effects requiring veterinary consultation are uncommon but may include prolonged skin irritation at the application site that worsens rather than improving over several days, lethargy extending beyond twenty-four to forty-eight hours, more significant gastrointestinal disturbance including notable appetite reduction or persistent soft stool, or behavioral changes such as unusual hiding or decreased social interaction. Signs suggesting gastrointestinal stasis, characterized by cessation of eating, absence of fecal pellets, hunched posture, and obvious discomfort, constitute an emergency requiring immediate veterinary attention regardless of suspected cause. Any concerning symptoms that persist or worsen should prompt veterinary evaluation.

Serious side effects of selamectin in guinea pigs are rare when the medication is used appropriately but reflect the potential consequences of the drug's mechanism of action on nervous system function at excessive exposure levels. Neurological toxicity from significant overdose could manifest as depression, ataxia or incoordination, tremors, and in severe cases, more serious neurological impairment. These severe effects would result from substantial overdosing far beyond recommended amounts. Because selamectin is provided in pre-measured doses and has a wide safety margin, serious toxicity is very uncommon with appropriate use. Any guinea pig showing neurological symptoms after selamectin application requires immediate veterinary evaluation, though such occurrences are rare.

Rare side effects and long-term concerns with selamectin in guinea pigs are minimal given the extensive clinical experience with this medication in small mammals. Application site reactions may occasionally persist or recur with repeated treatments in sensitive individuals. Allergic or hypersensitivity reactions to selamectin or the carrier solution are possible but uncommon. Long-term monthly use for prevention in multi-pet households or for guinea pigs with recurrent parasite exposure has been practiced without documented cumulative toxicity. Any concerning symptoms during or after selamectin treatment warrant veterinary consultation. The overall message regarding side effects is that selamectin is remarkably well-tolerated by guinea pigs, with adverse effects being the exception rather than the rule when proper dosing is observed.

Known allergy or hypersensitivity to selamectin or other macrocyclic lactone antiparasitics including ivermectin and moxidectin represents a contraindication to selamectin use in guinea pigs. If a guinea pig has previously experienced an adverse reaction to any macrocyclic lactone, including skin reactions, neurological symptoms, or other concerning effects, the entire class of medications should generally be avoided and alternative antiparasitics from different chemical classes should be considered. Cross-reactivity among macrocyclic lactones is expected given their shared mechanism and chemical relationships. Sensitivity to the carrier solution or other inactive ingredients in selamectin products is also possible and would contraindicate use. Owners should always inform their veterinarian of any previous medication reactions.

Organ dysfunction considerations for selamectin use in guinea pigs primarily involve liver function, as the medication undergoes hepatic metabolism. Guinea pigs with known liver disease or suspected hepatic dysfunction may process selamectin differently than healthy animals, potentially leading to altered drug exposure. While topical selamectin has a wide safety margin, animals with compromised liver function may warrant additional monitoring or consideration of alternative treatments. Kidney function is less critical for selamectin handling but should be considered in guinea pigs with known renal disease. Pre-treatment blood work can help assess organ function in guinea pigs with known health conditions or those over three years of age where subclinical organ changes become more likely.

Life stage restrictions for selamectin in guinea pigs include consideration of pregnant and nursing animals, though selamectin has demonstrated a relatively favorable safety profile during these periods in other species. Treatment of pregnant sows should involve discussion with the veterinarian to weigh the risks of parasitic infestation against any theoretical medication risks, with treatment generally considered acceptable when infestation threatens maternal health. Nursing sows can typically receive selamectin, though some transfer to nursing pups may occur. Very young guinea pig pups may receive some exposure if nursing from treated mothers, and direct treatment of very young animals should be approached conservatively. The veterinarian can provide guidance on age-appropriate treatment initiation.

Guinea pig-specific contraindications for selamectin are not extensively documented beyond general macrocyclic lactone considerations, as the medication has demonstrated good safety in this species. Application to broken or severely inflamed skin is generally not recommended, as absorption may be altered and irritation may be worsened. Guinea pigs who groom the application site despite its location between the shoulder blades may ingest medication, which is not ideal though selamectin has oral safety as well. Concurrent use of other antiparasitic medications should be disclosed to the veterinarian to avoid potential additive effects. Complete disclosure of the guinea pig's medical history, current medications including vitamin C supplementation, and any previous adverse reactions ensures the veterinarian can make fully informed treatment decisions.

Disclosure of all current medications, supplements, and treatments to the exotic veterinarian is essential before initiating selamectin therapy for parasitic conditions. This includes prescription medications, over-the-counter products, vitamin supplements including the essential vitamin C, herbal preparations, and any other substances the guinea pig receives. Drug interactions can affect selamectin's absorption, distribution, metabolism, or excretion, potentially altering efficacy or safety. Even products that seem unrelated to antiparasitic treatment can potentially interact with selamectin or affect the guinea pig's overall tolerance of the medication. The veterinarian can assess potential interactions and adjust the treatment plan if necessary.

Major drug class interactions with selamectin involve medications that affect metabolic pathways or blood-brain barrier permeability. P-glycoprotein inhibitors could theoretically increase selamectin penetration into the central nervous system, though such medications are rarely encountered in guinea pig practice. Concurrent use of other antiparasitic medications should be discussed with the veterinarian due to potential additive effects, though combination therapy may occasionally be employed deliberately for resistant or severe infestations. Drugs affecting liver enzyme function could potentially alter selamectin metabolism, though significant clinical interactions are not well-documented in guinea pigs. Vitamin C supplementation, which is essential and should never be discontinued in guinea pigs, does not interact negatively with selamectin.

Supplement and dietary interactions with selamectin are minimal, and guinea pigs should continue their normal diet and all necessary supplementation during treatment. The critical vitamin C that guinea pigs require daily does not interact with selamectin and must be maintained for immune function and tissue health. Calcium and other mineral supplements can continue without expected interaction. Probiotic supplementation may support gut health during any period of illness or treatment. Timing of selamectin application relative to feeding is not significant. Herbal supplements should be reported to the veterinarian as some may have effects on drug metabolism, though specific interactions with selamectin in guinea pigs are not documented. Maintaining normal dietary routine during treatment supports overall guinea pig health.

Monitoring for drug interactions during selamectin treatment involves observing for any unexpected effects suggesting altered drug activity or tolerance. Signs of potential interaction include unexpected changes in efficacy, unusual adverse effects, or altered response to concurrent medications. Any concerns should prompt veterinary consultation. The topical application route and monthly dosing interval provide straightforward treatment monitoring. Maintaining documentation of all medications, supplements, and topical products being used facilitates effective veterinary oversight. Normal diet, routine, and supplementation during treatment help distinguish any drug effects from other causes of behavioral or health changes in the guinea pig.

General precautions for selamectin use in guinea pigs include ensuring accurate body weight measurement for proper dose determination and correct application technique for optimal absorption. Weighing the guinea pig using a gram scale before obtaining the prescription ensures the veterinarian can calculate the appropriate dose. Proper application to exposed skin between the shoulder blades maximizes transdermal absorption and prevents ingestion through grooming. The application site should be dry, and bathing should be avoided for several days after treatment to prevent washing off unabsorbed medication. Monitoring for any signs of gastrointestinal stasis, which can occur during any illness or stressful period in guinea pigs, should continue even though selamectin is well-tolerated.

Breed-specific concerns with selamectin treatment vary primarily based on coat characteristics that affect application technique. Skinny pigs with their hairless or nearly hairless skin require attention to application site selection, as the medication applied to bare skin may absorb differently than when applied to skin under fur. The lack of hair also eliminates any barrier between the medication and environmental contact until the solution dries completely. Long-haired breeds including Peruvians, Silkies, and Texels require thorough parting of the coat to ensure the medication reaches the skin rather than remaining on the hair where it cannot absorb properly. Abyssinian guinea pigs with their rosette patterns may similarly require attention to proper application. All breeds benefit equally from selamectin's efficacy once properly applied.

Environmental precautions during selamectin treatment for ectoparasites include thorough cleaning of the guinea pig's habitat to eliminate environmental contamination with parasites and eggs. Complete bedding replacement and cage surface cleaning complement the medication treatment by removing parasites from the environment that could cause reinfestation. All guinea pigs in the household should receive treatment simultaneously even if asymptomatic, as untreated animals can harbor parasites and serve as reinfestation sources. The monthly interval between selamectin applications provides time for environmental recontamination if cleaning is not thorough, making comprehensive habitat sanitation important for treatment success. The treated guinea pig should be kept away from cage mates until the application site is dry.

Monitoring during selamectin treatment should include daily observation for changes in behavior, appetite, activity level, and skin condition at the application site, particularly in the days following each application. Regular weighing helps detect weight loss that might indicate reduced food intake. Tracking hay and pellet consumption, water intake, and fecal pellet production identifies potential problems early. Signs of treatment efficacy include resolution of scratching and itching behavior, improvement in skin condition with resolution of lesions, and regrowth of hair in previously affected areas. Signs of potential problems requiring veterinary attention include persistent or worsening application site reactions, unusual lethargy, or any gastrointestinal disturbance.

Special population considerations for selamectin include awareness that senior guinea pigs over three years of age may have subclinical changes in organ function that could theoretically affect drug handling, though selamectin's wide safety margin generally accommodates such changes without significant concern. Young guinea pigs may receive some exposure through nursing if their mother is treated. Immunocompromised guinea pigs may benefit from parasite treatment while warranting general health monitoring during therapy. Guinea pigs with chronic conditions such as heart disease or respiratory problems may need coordination of antiparasitic treatment with management of other health issues. Pregnant and nursing sows can generally receive selamectin when the benefits of treating parasitic infestation outweigh theoretical risks, with veterinary guidance on timing and approach.

Storage requirements for selamectin products include keeping the medication at room temperature, typically below eighty-six degrees Fahrenheit, protected from direct light and stored in the original packaging until use. Selamectin tubes should remain sealed until the application time, as exposure to air may affect the product. The medication should be stored away from the guinea pig's habitat and away from food preparation areas, in a location inaccessible to children and other pets. Revolution products have manufacturer-specified expiration dates that should be verified before each use to ensure product efficacy. Storage in excessively hot locations, such as inside vehicles or near heat sources, should be avoided as extreme temperatures may degrade the medication.

Formulation-specific considerations for selamectin storage relate to the packaging of individual dose tubes. Once a tube is opened, it should be used promptly, as the carrier solution may evaporate over time if left exposed. For guinea pigs who receive only a portion of a tube based on their body weight, the veterinarian may provide guidance on whether the remainder can be stored briefly for a second guinea pig or subsequent application, though using fresh product for each application is generally preferred. The tube applicator tip should be handled carefully to prevent contamination. Signs that the product may be compromised include unusual color, consistency changes, or a tube that appears to have leaked or been exposed to extreme conditions.

Safety and disposal considerations for selamectin emphasize keeping the product secured away from children, other pets, and the guinea pigs themselves. While selamectin has a wide safety margin, accidental ingestion or exposure should be avoided. After application, the treated guinea pig should be kept away from cage mates until the application site has dried to prevent secondary exposure through grooming or contact. Unused or expired selamectin should be disposed of properly through veterinary pharmaceutical waste programs, drug take-back programs, or household hazardous waste collection rather than being discarded in regular trash or poured down drains. Empty tubes should be disposed of according to packaging instructions. Hands should be washed after handling the medication and after handling the treated guinea pig.

Most guinea pig breeds tolerate selamectin treatment excellently, with no documented breed-specific sensitivities or increased risk of adverse effects based on breed characteristics. The diversity of guinea pig breeds primarily involves coat type, color, and pattern rather than significant metabolic differences affecting drug handling. This consistency allows selamectin to be used confidently across all guinea pig varieties. Veterinarians experienced with guinea pigs recognize that breed considerations for selamectin relate primarily to practical aspects of application technique and visualization of parasites and treatment response rather than differences in drug safety or efficacy.

Specific breed characteristics influence the practical aspects of selamectin application and monitoring. Skinny pigs with their hairless or nearly hairless skin present unique considerations because the medication is applied directly to exposed skin without the fur covering present in other breeds. Care should be taken to ensure the application site can dry without environmental contamination, and the visible skin allows easy monitoring for any local reactions. Long-haired breeds including Peruvians, Silkies, and Texels require thorough parting of the luxurious coat to ensure selamectin reaches the skin surface. These same breeds may obscure skin pathology and treatment response under their coats, making careful examination important. Abyssinian guinea pigs with their characteristic rosettes and American guinea pigs with smooth coats present intermediate considerations for application technique and monitoring.

Size considerations for selamectin dosing relate to individual guinea pig variation rather than breed-specific size differences. Guinea pigs range from approximately five hundred grams for smaller adults to over one thousand two hundred grams for larger individuals, and the veterinarian selects the appropriate Revolution product size and calculates the portion to apply based on actual body weight. Accurate weighing using a gram scale ensures proper dosing. The veterinarian's familiarity with Revolution products and guinea pig dosing ensures appropriate product selection. Smaller guinea pigs may receive a portion of the smallest available tube, while larger guinea pigs may require a larger amount.

Age considerations for selamectin use span the guinea pig lifespan with generally consistent safety at appropriate doses. Young guinea pig pups nursing from treated mothers may receive some drug exposure through milk, though this is generally not considered problematic given selamectin's safety profile. Direct treatment of very young guinea pigs should follow veterinary guidance regarding minimum age for application. Senior guinea pigs over three to four years of age may have subclinical changes in organ function that could theoretically affect drug handling, though selamectin's wide safety margin generally accommodates age-related changes without significant concern. Veterinary guidance ensures age-appropriate treatment for guinea pigs at any life stage.

Same-class alternatives to selamectin for guinea pig ectoparasite treatment include other macrocyclic lactone antiparasitics, primarily ivermectin and moxidectin. Ivermectin, most commonly administered by subcutaneous injection, remains the most frequently used medication in this class and offers an alternative for guinea pigs who may not tolerate topical application or when the veterinarian prefers injectable treatment. Moxidectin provides another option with pharmacokinetic differences including extended duration of action. These related medications share the same mechanism of action and similar spectrum of activity, allowing substitution when preferred for individual patient or practical reasons. The choice among macrocyclic lactones often depends on veterinary preference, available products, owner comfort with different application methods, and patient factors.

Different class options for treating ectoparasites in guinea pigs exist but are generally considered second-line compared to the macrocyclic lactones due to less favorable safety profiles or practical limitations. Fipronil can be used with significant dilution and caution but carries higher risk than selamectin. Pyrethrin and pyrethroid products are generally not preferred for guinea pigs due to safety concerns. Environmental treatments with premise sprays may complement systemic therapy but do not replace direct treatment of the guinea pig. For specific internal parasites that macrocyclic lactones may not optimally address, alternative anthelmintics such as fenbendazole may be more appropriate. Veterinary guidance ensures selection of the most appropriate medication for each clinical situation.

Complementary therapies and supportive care during selamectin treatment for parasitic infestations include maintaining optimal nutrition with emphasis on vitamin C supplementation, which guinea pigs cannot synthesize and require daily for immune function, tissue healing, and overall health. Critical Care or similar recovery feeding may support guinea pigs whose appetite has been diminished by severe parasitic infestations. Probiotic supplementation supports healthy gut flora during illness and treatment. Environmental management including thorough cage cleaning, complete bedding replacement, and treatment of all in-contact guinea pigs eliminates reinfestation sources and optimizes treatment success. Gentle bathing with guinea pig-safe products may provide comfort but is not required for treatment efficacy and should be timed to avoid interfering with selamectin absorption. Any medication changes or additions should only occur under veterinary guidance.