Furosemide (Lasix) - diuretic

Furosemide, commonly known by its brand name Lasix, is a potent loop diuretic that serves as a cornerstone medication in the management of fluid overload conditions in small mammals. This medication belongs to the sulfonamide-derived loop diuretic class and works by inhibiting sodium and chloride reabsorption in the ascending loop of Henle within the kidneys. By blocking these transport mechanisms, furosemide produces rapid and substantial diuresis, making it invaluable for emergency situations involving pulmonary edema, pleural effusion, and other life-threatening fluid accumulation conditions in exotic small mammals including ferrets, guinea pigs, chinchillas, rabbits, rats, and other species.

The development of furosemide dates back to the 1960s when it was first synthesized as a more potent alternative to existing diuretics. Its introduction to veterinary medicine followed shortly after its human medical applications were established, and it has since become one of the most frequently prescribed diuretics across all veterinary species. In small mammal medicine, furosemide gained particular importance as exotic veterinary practice evolved and practitioners began managing complex cardiac and renal conditions in these diminutive patients. The medication's rapid onset of action and predictable pharmacological effects have made it essential in both emergency and chronic disease management.

Furosemide is available in multiple formulations suitable for small mammal administration, including injectable solutions for acute management, oral tablets that can be crushed or compounded, and specially compounded oral liquids that facilitate accurate dosing in tiny patients. The injectable form provides the fastest onset of action and is preferred in emergency situations, while oral formulations are typically used for chronic management of heart failure and other ongoing conditions. Compounding pharmacies play a vital role in small mammal medicine by creating appropriately concentrated liquid formulations that allow for precise dosing in animals weighing only a few hundred grams.

The overall effectiveness and safety profile of furosemide in small mammals is well-established through decades of clinical use, though formal pharmacokinetic studies in many exotic species remain limited. The medication is generally well-tolerated when properly dosed and monitored, with electrolyte imbalances representing the primary concern during extended therapy. Unlike many medications used in small mammals, furosemide does not carry the risk of fatal dysbiosis that plagues antibiotic selection in hindgut fermenters, making it relatively straightforward to incorporate into treatment protocols. However, careful monitoring of hydration status, renal function, and electrolyte balance remains essential, particularly in critically ill patients or those requiring long-term diuretic therapy.

Furosemide serves multiple critical therapeutic roles in small mammal medicine, with its primary indication being the management of congestive heart failure and associated fluid accumulation. In ferrets, which are particularly prone to cardiac disease including dilated cardiomyopathy and valvular disease, furosemide often forms the foundation of heart failure management protocols. The medication effectively reduces pulmonary edema that develops when the failing heart cannot adequately circulate blood, relieving respiratory distress and improving quality of life. Guinea pigs also develop cardiac conditions that benefit from diuretic therapy, and furosemide helps manage the fluid retention that accompanies heart disease in these sensitive herbivores.

Beyond cardiac applications, furosemide is indicated for the treatment of various forms of pathological fluid accumulation regardless of the underlying cause. Ascites, the accumulation of fluid within the abdominal cavity, may develop secondary to liver disease, neoplasia, or other conditions in small mammals, and furosemide helps mobilize this excess fluid. Pleural effusion, fluid accumulation around the lungs, represents a particularly urgent indication for furosemide therapy as it directly compromises respiratory function. The medication is also valuable in managing edema associated with nephrotic syndrome and certain kidney diseases, though careful consideration must be given to overall renal function before initiating therapy.

In emergency situations, furosemide serves as a critical intervention for acute pulmonary edema from various causes. Small mammals experiencing respiratory distress from fluid accumulation require rapid diuresis to survive, and injectable furosemide provides the fastest route to achieving therapeutic effect. This emergency application extends to post-anesthetic complications, acute heart failure decompensation, and fluid overload from overly aggressive intravenous or subcutaneous fluid administration. The medication's predictable onset of action makes it invaluable in these time-sensitive scenarios where minutes can determine survival outcomes.

Off-label applications of furosemide in small mammals include management of certain types of hypertension, though this indication is less common than in larger veterinary species. Some practitioners utilize furosemide to help manage cerebral edema in neurological emergencies, capitalizing on its ability to reduce overall body water content. The medication may also be employed diagnostically to assess renal function by evaluating the diuretic response, though this application requires careful interpretation. In ferrets with insulinoma undergoing surgical management, furosemide may be used perioperatively to manage any fluid complications that arise.

When selecting furosemide over alternative diuretics, practitioners typically consider the urgency of the clinical situation and the degree of diuresis required. Furosemide produces more substantial diuresis than thiazide diuretics, making it the preferred choice for significant fluid overload conditions. Its relatively short duration of action allows for fine control of the diuretic effect when needed, though this same characteristic necessitates more frequent dosing compared to longer-acting alternatives. The medication is typically chosen first-line for heart failure management in small mammals due to its proven efficacy, established dosing guidelines, and widespread availability in formulations suitable for these tiny patients.

Dosing of furosemide in small mammals requires careful consideration of species-specific factors, clinical severity, and individual patient variables, making consultation with an exotic veterinarian essential before initiating therapy. General dosing principles emphasize starting with lower doses and titrating upward based on clinical response, as the therapeutic window may be narrower in small exotic species than in dogs and cats. The goal of therapy is to achieve adequate diuresis to resolve clinical signs while minimizing the risk of dehydration and electrolyte disturbances. Exotic veterinarians familiar with small mammal physiology can best determine appropriate starting doses and adjustment strategies based on each patient's specific condition and response to treatment.

The route of administration significantly impacts the onset, intensity, and duration of furosemide's diuretic effect. Intravenous administration provides the most rapid onset of action, typically within five minutes, making it the preferred route for acute emergencies when immediate diuresis is required. Intramuscular administration offers intermediate onset times and may be more practical in small mammals where venous access proves challenging. Subcutaneous administration, while slower in onset, provides a more gradual diuretic effect and is commonly used for maintenance therapy or when the patient can tolerate a less aggressive approach. Oral administration is typically reserved for chronic management once the patient is stabilized, though absorption may be affected by gastrointestinal factors.

Frequency of administration varies considerably based on the clinical scenario and the patient's response to initial therapy. Emergency situations may require furosemide administration every one to four hours until the patient stabilizes, with gradual lengthening of the dosing interval as clinical improvement occurs. Chronic heart failure management typically involves twice or three times daily oral dosing, adjusted based on the patient's respiratory rate and effort, hydration status, and overall comfort. Some patients with mild disease may eventually be maintained on once-daily dosing, while others with more severe conditions require more frequent administration throughout their lives.

Species-specific considerations profoundly influence furosemide dosing decisions in small mammals. Ferrets generally tolerate furosemide well and may require dosing frequencies and approaches similar to those used in cats. Guinea pigs and chinchillas, as hindgut fermenters with sensitive gastrointestinal systems, require careful monitoring for any adverse effects on gut motility or appetite during diuretic therapy. Hamsters and other very small rodents present particular challenges due to their tiny body size, rapid metabolism, and difficulty in accurately measuring liquid medications. Hedgehogs and sugar gliders have their own unique physiological characteristics that may affect drug handling and require experienced exotic veterinary guidance.

Compounding of furosemide into appropriate concentrations represents a critical aspect of small mammal therapeutics given the minute doses required. Commercial tablet strengths are typically far too large for direct administration to most small mammals, necessitating either tablet splitting with significant potential for inaccuracy or compounding into flavored liquid formulations. Reputable compounding pharmacies can prepare furosemide suspensions in concentrations that allow for accurate measurement of appropriate doses using small syringes. The stability of compounded formulations varies based on the specific preparation, and prescribing veterinarians should provide guidance on beyond-use dating and storage requirements.

Administration tips for owners include techniques for stress reduction during medication delivery, accurate measurement using appropriate syringes, and recognition of signs requiring veterinary attention. Oral liquid medications are typically administered by gently restraining the small mammal, inserting a syringe tip into the side of the mouth behind the incisors, and slowly delivering the medication to allow swallowing. Owners should be counseled on the expected increase in urination following furosemide administration and the importance of ensuring adequate water availability. Signs of excessive diuresis including lethargy, decreased appetite, or reduced urine output should prompt immediate veterinary consultation to prevent complications from dehydration or electrolyte depletion.

The most common side effects of furosemide therapy in small mammals relate to the medication's primary pharmacological action of promoting fluid and electrolyte excretion. Dehydration represents a significant concern, particularly in small mammals with high metabolic rates and limited body water reserves. Signs of excessive diuresis include decreased skin turgor, sunken eyes, tacky mucous membranes, and reduced urine output despite continued medication administration. Weight loss during acute therapy may reflect appropriate fluid mobilization, but continued weight loss during chronic treatment often indicates excessive diuresis requiring dose adjustment. Close monitoring of hydration status, ideally including periodic body weight measurements, helps detect dehydration before it becomes clinically significant.

Electrolyte imbalances constitute the most important metabolic side effects of loop diuretic therapy. Potassium depletion occurs because furosemide increases potassium excretion along with sodium and water, potentially leading to hypokalemia with associated muscle weakness, cardiac arrhythmias, and lethargy. Sodium and chloride depletion may also occur, particularly with aggressive or prolonged diuretic therapy. Magnesium and calcium losses, while less commonly clinically significant, can contribute to various metabolic disturbances. Small mammals receiving long-term furosemide therapy often benefit from periodic electrolyte monitoring, though obtaining sufficient blood samples from tiny patients presents practical challenges that may limit this testing.

Gastrointestinal effects of furosemide are generally mild but warrant attention in small mammal patients. Decreased appetite may occur, particularly if dehydration or electrolyte imbalances develop. In hindgut fermenters such as guinea pigs and chinchillas, any reduction in food intake raises concerns about secondary gastrointestinal complications including stasis. Owners should monitor food consumption carefully and report any significant decreases to the prescribing veterinarian promptly. Ensuring adequate hydration and electrolyte balance typically prevents most gastrointestinal complications, but affected patients may require supportive care including fluid supplementation and appetite stimulation.

Serious and rare side effects of furosemide include ototoxicity, particularly when administered rapidly intravenously or when combined with other potentially ototoxic medications such as aminoglycoside antibiotics. Hearing loss in small mammals may be difficult to detect clinically but represents a genuine risk with high-dose or prolonged therapy. Acute kidney injury can occur if excessive diuresis leads to severe volume depletion and decreased renal perfusion, emphasizing the importance of careful monitoring during initial therapy. Allergic reactions are possible as furosemide is a sulfonamide derivative, though true hypersensitivity is uncommon. Very rarely, blood dyscrasias including anemia, leukopenia, and thrombocytopenia have been reported in other species.

Owners should be educated on warning signs that necessitate immediate veterinary contact when their small mammal is receiving furosemide therapy. Marked lethargy or weakness beyond what might be expected from the underlying disease warrants prompt evaluation for dehydration or electrolyte abnormalities. Refusal to eat, particularly in hindgut fermenters where continued gastrointestinal motility is essential, requires urgent attention. Collapse, seizures, or severe respiratory distress despite appropriate therapy may indicate either inadequate disease control or complications of treatment. Any sudden worsening of the patient's condition should prompt veterinary consultation rather than at-home dose adjustments, as the underlying cause requires professional assessment.

Furosemide is contraindicated in small mammals with anuria or severe oliguria where urine production has essentially ceased, as the medication cannot produce its therapeutic effect without functional nephrons and may worsen the underlying condition. Complete urinary obstruction similarly precludes furosemide use until the obstruction is relieved, as promoting fluid excretion into a blocked system creates dangerous pressure complications. Severe uncorrected electrolyte depletion, particularly hypokalemia or hyponatremia, should be addressed before initiating or continuing furosemide therapy to prevent exacerbation of these potentially life-threatening imbalances. Patients with known hypersensitivity to furosemide or other sulfonamide derivatives should not receive this medication.

Certain medical conditions warrant extreme caution or contraindicate furosemide use depending on severity. Severe hepatic impairment with hepatic encephalopathy may be worsened by the electrolyte disturbances associated with diuretic therapy, particularly hypokalemia which can precipitate hepatic coma. Severe dehydration from any cause should be corrected before initiating diuretic therapy, as furosemide administration to an already volume-depleted patient risks acute kidney injury and cardiovascular collapse. Conditions associated with severe hypovolemia, including shock from any cause, generally contraindicate diuretic administration until adequate volume resuscitation has occurred. Diabetes mellitus may be complicated by furosemide therapy, as the medication can affect glucose metabolism and electrolyte balance.

Age-related and reproductive status considerations affect furosemide use in small mammal patients. Very young animals with immature renal function may handle diuretics differently than adults, requiring additional caution and close monitoring. Geriatric patients often have reduced renal reserve and may be more susceptible to complications from aggressive diuresis. Pregnant small mammals present particular concerns, as excessive diuresis could compromise placental perfusion and fetal development, and the medication does cross the placenta to reach fetal circulation. Nursing mothers excrete furosemide in milk, potentially affecting nursing offspring through both direct drug effects and reduced milk production secondary to maternal dehydration.

Situations where furosemide should not be used or should be used only with extreme caution include patients who cannot be adequately monitored for response to therapy and development of complications. The medication should not be administered at home without proper veterinary guidance and follow-up, as complications can develop rapidly. Small mammals with poor venous access and limited ability to receive emergency interventions require careful consideration of the risks and benefits of diuretic therapy. Patients who are eating and drinking poorly may not tolerate the additional fluid losses induced by diuretics, making supportive care addressing the underlying inappetence a priority before initiating furosemide. When owners are unable to recognize early signs of complications or return promptly for recheck examinations, alternative management strategies or careful patient selection becomes essential.

Furosemide interacts with numerous other medications through various mechanisms including additive effects, altered excretion, and pharmacodynamic interactions. Concurrent use of other diuretics, including thiazide diuretics and potassium-sparing agents, requires careful consideration of the combined effects on fluid and electrolyte balance. While spironolactone is sometimes intentionally combined with furosemide to offset potassium losses, inappropriate combinations of diuretic agents can lead to severe dehydration and electrolyte abnormalities. Angiotensin-converting enzyme inhibitors such as enalapril, commonly used alongside furosemide for heart failure management, may potentiate hypotensive effects and affect renal function, necessitating careful monitoring when initiating combination therapy.

Several medication classes interact with furosemide to increase the risk of adverse effects. Aminoglycoside antibiotics including gentamicin and amikacin share ototoxic potential with furosemide, and concurrent use significantly increases the risk of hearing damage. Non-steroidal anti-inflammatory drugs may reduce furosemide's diuretic efficacy by inhibiting prostaglandin synthesis in the kidneys, potentially compromising disease control in patients requiring both medications. Corticosteroids can exacerbate potassium losses when combined with furosemide, increasing the risk of clinically significant hypokalemia. Digoxin toxicity becomes more likely in the presence of furosemide-induced hypokalemia, making potassium monitoring particularly important when these medications are used together.

Interactions with supplements and dietary factors deserve consideration in small mammal patients receiving furosemide. Potassium supplementation may be beneficial for patients on chronic furosemide therapy, but the amount must be carefully balanced against the degree of potassium loss to avoid hyperkalemia. Sodium intake affects diuretic efficacy, with high-sodium diets potentially reducing the effectiveness of furosemide therapy. Calcium and magnesium supplementation may be warranted in some patients on long-term therapy, though requirements vary considerably between species and individuals. Herbal supplements with diuretic properties should be avoided during furosemide therapy due to unpredictable additive effects.

Safe combinations with furosemide in small mammal cardiovascular therapy typically include the concurrent use of pimobendan, enalapril or other ACE inhibitors, and sometimes spironolactone as part of comprehensive heart failure management protocols. These combinations require initial dose adjustments and careful monitoring during the stabilization period, but represent evidence-based approaches to managing cardiac disease. Antibiotics from safe classes for the species involved can generally be administered alongside furosemide when infection treatment is required. Pain medications including opioids are typically compatible with furosemide therapy, though NSAID combinations warrant the caution described above. The prescribing exotic veterinarian should be informed of all medications and supplements the patient receives to evaluate potential interactions and adjust the treatment plan accordingly.

Unlike many antibiotics, furosemide does not carry a risk of fatal dysbiosis in hindgut-fermenting small mammals, eliminating one of the major concerns that complicates medication selection in guinea pigs, chinchillas, rabbits, and hamsters. However, the indirect effects of diuretic therapy on gastrointestinal function warrant attention in these sensitive species. Dehydration reduces gut motility and can precipitate or worsen gastrointestinal stasis, a life-threatening condition in herbivorous small mammals. Electrolyte imbalances, particularly potassium depletion, similarly affect smooth muscle function throughout the body including the gastrointestinal tract. Ensuring adequate hydration and monitoring appetite and fecal output remain important components of furosemide therapy in hindgut fermenters.

Species-specific warnings emphasize the unique physiological characteristics that affect furosemide therapy across different small mammal groups. Ferrets with cardiac disease often have concurrent conditions such as insulinoma or adrenal disease that may affect their overall stability during diuretic therapy and require integrated management approaches. Guinea pigs and chinchillas require careful attention to continued food and water intake throughout furosemide therapy, with prompt intervention if appetite decreases. Hamsters and other small rodents are particularly susceptible to rapid dehydration due to their tiny body size and high surface area to volume ratio. Hedgehogs may become more prone to torpor and reduced activity when stressed by illness and treatment, complicating assessment of their response to therapy.

Monitoring requirements during furosemide therapy include regular assessment of hydration status, body weight, respiratory rate and effort, and overall clinical condition. Baseline body weight provides a reference point for detecting both fluid loss from effective diuresis and excessive fluid depletion from overtreatment. Respiratory parameters help evaluate the effectiveness of therapy in patients being treated for pulmonary edema or pleural effusion. Blood work including renal values and electrolytes provides objective data on metabolic status, though sample volume limitations may restrict testing frequency in very small patients. Home monitoring by owners should include daily assessment of appetite, activity level, urine output, and any concerning signs such as weakness or labored breathing.

Human safety considerations during furosemide handling are relatively minimal compared to many other veterinary medications. The medication is not absorbed well through intact skin, though hand washing after handling tablets or liquids is prudent standard practice. Compounded liquid formulations may contain flavoring agents that could cause minor irritation if splashed into eyes, making careful handling during syringe preparation advisable. Accidental ingestion of small amounts would likely produce only mild diuretic effects in healthy adults, though medical advice should be sought if significant quantities are consumed or if the exposed person has underlying medical conditions. Keeping medications stored securely away from children remains an essential safety practice.

Storage of furosemide during ongoing treatment courses requires attention to the specific formulation being used. Commercial injectable solutions and tablets generally maintain stability under standard room temperature storage conditions when protected from light. Compounded oral preparations may have variable stability depending on the specific formulation, with beyond-use dates typically ranging from days to weeks depending on ingredients and storage conditions. Medications should be stored according to the compounding pharmacy's instructions and discarded after expiration. During treatment, having an adequate supply on hand prevents interruptions that could compromise disease management.

Proper storage of furosemide maintains medication potency and ensures therapeutic efficacy throughout the treatment period. Commercial furosemide tablets should be stored at controlled room temperature, generally between fifteen and thirty degrees Celsius, in their original containers to protect from light and moisture. Injectable formulations require protection from light and should be examined before use for any discoloration or particulate matter that might indicate degradation. Once opened, multi-dose injectable vials maintain stability for the period indicated on the manufacturer's labeling, typically fourteen to thirty days depending on the product. Refrigeration is not typically required for commercial furosemide preparations unless specifically indicated by the manufacturer.

Compounded furosemide preparations, which represent the most common formulations used in small mammal medicine, have stability profiles that vary based on the specific compounding formula and preparation method. Compounding pharmacies provide beyond-use dating based on their stability testing or published stability data for similar preparations. Typical beyond-use dates for compounded furosemide oral suspensions range from fourteen to ninety days depending on the formulation, with refrigeration often extending stability. Owners should follow storage instructions provided by the compounding pharmacy precisely, including refrigeration requirements and protection from light. Shaking liquid preparations before each use ensures uniform concentration throughout the bottle and accurate dosing.

Safe handling and disposal of furosemide follows standard medication safety practices appropriate for a prescription pharmaceutical without significant toxicity concerns. Unused or expired medication should not be disposed of through regular household trash or by flushing down drains, as pharmaceutical contamination of water supplies represents an environmental concern. Many veterinary clinics and pharmacies accept unused medications for proper disposal, and some communities offer pharmaceutical take-back programs. If no take-back options are available, mixing medications with unpalatable substances such as coffee grounds and placing in sealed containers before disposal helps prevent accidental ingestion by animals or children. Empty medication containers should be disposed of after removing or obscuring personal prescription information.

Hamsters, gerbils, mice, and rats each present unique considerations when furosemide therapy is required. These small rodents have rapid metabolic rates that may affect drug clearance and necessitate attention to dosing frequency. Their tiny body size means that even small absolute fluid losses represent significant percentages of total body water, making dehydration a constant concern during diuretic therapy. Rats are among the most commonly treated of these species due to their popularity as pets and relatively robust nature, and they generally tolerate furosemide well when appropriately dosed. Hamsters and gerbils present greater challenges due to their smaller size and the difficulty of obtaining compounded preparations in sufficiently dilute concentrations. Mice are rarely treated with furosemide due to their extremely small size and short lifespan, though therapeutic intervention is not impossible in committed cases.

Guinea pigs and chinchillas share characteristics as hindgut-fermenting herbivores that affect their management during furosemide therapy. Their gastrointestinal systems depend on continuous fiber intake and appropriate hydration to maintain motility, making any threat to appetite or water balance potentially serious. Furosemide does not directly disrupt their gut flora as dangerous antibiotics would, but dehydration and reduced food intake secondary to illness or treatment stress can precipitate gastrointestinal stasis. Guinea pigs' vitamin C requirements continue during illness and treatment, and this essential nutrient should not be neglected when managing cardiac or other conditions requiring diuretics. Chinchillas' sensitivity to heat stress may complicate management if they become dehydrated during furosemide therapy, as their thermoregulatory mechanisms depend partly on adequate hydration.

Ferrets represent the small mammal species most commonly requiring furosemide therapy due to their predisposition to cardiac disease, particularly dilated cardiomyopathy and valvular insufficiency. Their physiology differs substantially from rodents and hindgut fermenters, more closely resembling cats in many respects including drug handling. Ferrets can develop heart failure requiring aggressive initial stabilization with injectable furosemide followed by long-term oral maintenance therapy. Their relatively larger size compared to other small mammals allows for easier medication administration and monitoring, though they still represent challenging patients compared to dogs and cats. Ferrets with concurrent diseases such as insulinoma or adrenal disease require integrated management approaches that account for the effects of cardiac medications on their other conditions.

Hedgehogs and sugar gliders are less commonly treated with furosemide but may require diuretic therapy for various conditions. Hedgehogs develop cardiac disease and may benefit from furosemide as part of heart failure management, though their tendency to ball up defensively can complicate medication administration and clinical assessment. Their spines require careful handling during treatment, and stress reduction strategies help facilitate ongoing therapy. Sugar gliders' very small body size necessitates extremely dilute compounded preparations and meticulous attention to accurate dosing. Their unique dietary requirements and social nature should be considered when managing chronic diseases, as stress from isolation or handling may affect their response to therapy.

Within the diuretic class, alternatives to furosemide include other loop diuretics and agents from different diuretic categories. Torsemide is another loop diuretic with longer duration of action that may be useful in some small mammal patients, though clinical experience is more limited than with furosemide. Hydrochlorothiazide and other thiazide diuretics provide milder diuresis and may be considered for patients with less severe fluid retention or those intolerant of loop diuretics, though their availability in appropriate formulations for small mammals is limited. Spironolactone, a potassium-sparing diuretic, is often combined with furosemide rather than used as a replacement, providing complementary mechanisms of action and helping offset potassium losses.

For heart failure management in small mammals, furosemide is typically combined with other cardiac medications rather than used alone. Pimobendan has become increasingly important in ferret cardiology, providing positive inotropic effects that complement furosemide's fluid removal properties. Angiotensin-converting enzyme inhibitors such as enalapril or benazepril address neurohormonal activation in heart failure and may reduce the diuretic requirements over time. Beta-blockers are used in specific cardiac conditions though less commonly than in dogs and cats. The combination of multiple cardiac medications allows for lower doses of each individual agent, potentially reducing side effects while optimizing disease control.

When fluid management is needed for conditions other than heart failure, alternative approaches may be appropriate depending on the underlying cause. Therapeutic paracentesis or thoracocentesis can provide immediate relief of ascites or pleural effusion without the systemic effects of diuretics, though fluid typically reaccumulates if the underlying cause persists. Albumin infusions may help maintain fluid in the vascular space in patients with hypoalbuminemia, though availability and cost limit their use in small mammals. Fluid restriction and dietary sodium modification represent adjunctive measures that complement pharmaceutical management. Ultimately, addressing the underlying cause of fluid accumulation, whether cardiac disease, renal disease, liver disease, or neoplasia, determines the most appropriate long-term management strategy.