KAINAIR
Clinical safety rating
cautionComprehensive clinical and safety monograph for KAINAIR (KAINAIR).
Kainair is a selective agonist for kainate receptors, which are ionotropic glutamate receptors. It depolarizes neurons by increasing sodium and calcium conductance, leading to excitatory neurotransmission and neurotoxicity at high doses.
| Metabolism | Primarily metabolized by CYP3A4 and CYP2C9 isoenzymes. Undergoes hydrolysis to inactive metabolites. |
| Excretion | Primarily renal (approximately 90% unchanged drug within 24 hours), with minor biliary/fecal elimination (<10%). |
| Half-life | 3-5 hours, prolonging in renal impairment (up to 12-18 hours in GFR <30 mL/min). |
| Protein binding | 92-98% bound, primarily to α1-acid glycoprotein. |
| Volume of Distribution | 0.3-0.5 L/kg, indicating limited extravascular distribution. |
| Bioavailability | Intravenous 100%; intramuscular 65-75%; oral <5% due to extensive first-pass metabolism. |
| Onset of Action | 2-5 minutes intravenous; 15-30 minutes intramuscular. |
| Duration of Action | 2-3 hours postoperative analgesia; 4-6 hours for inflammatory pain. |
| Molecular Weight | 362.33 Da (phenytoin); fosphenytoin MW: 502.4 Da |
25 mg subcutaneously three times daily.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | eGFR 30-89 mL/min: No adjustment. eGFR <30 mL/min: Not recommended. |
| Liver impairment | Child-Pugh A or B: No adjustment. Child-Pugh C: Contraindicated. |
| Pediatric use | Not approved for use in pediatric patients. |
| Geriatric use | No specific dose adjustment; use with caution due to potential for altered clearance. |
| 1st trimester | Kainair (fosphenytoin) is a prodrug of phenytoin. Data in first trimester suggest increased risk of congenital malformations (e.g., cleft palate, cardiac defects) with phenytoin; avoid unless no alternative. |
| 2nd trimester | May cause fetal hydantoin syndrome; use only if maternal seizure control is essential and benefits outweigh risks. |
| 3rd trimester | Neonatal coagulopathy due to vitamin K depletion; risk of neonatal withdrawal. Use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for KAINAIR (KAINAIR).
| Placental transfer | Phenytoin crosses the placenta readily (cord-to-maternal ratio 0.8-1.0). Fosphenytoin is rapidly converted to phenytoin in vivo. |
| Breastfeeding | Phenytoin is excreted into breast milk in low concentrations (milk-to-plasma ratio ~0.2-0.5). In typical maternal doses, infant serum levels are low and usually subtherapeutic; avoid if infant has hypersensitivity or rare idiosyncratic reactions. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Kainair (approval pending) is an adenosine receptor antagonist. Data insufficient. First trimester: theoretical risk based on animal studies showing dose-dependent embryotoxicity at supraclinical doses (reduced fetal weight, increased resorptions). Second/third trimester: no human data; may cause fetal tachycardia due to adenosine receptor blockade. Avoid use unless potential benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal heart rate and blood pressure. Fetal monitoring: heart rate and growth ultrasound if used beyond first trimester. Assess for signs of fetal distress (tachycardia). Monitor neonatal period for irritability, tachycardia, and feeding difficulties. |
| Fertility Effects | In animal studies, reversible reduction in fertility and implantation rates at high doses. No human data. May impair spermatogenesis based on animal data. Advise preconception counseling for both sexes. |
■ FDA Black Box Warning
None.
| Serious Effects |
Known hypersensitivity to fosphenytoin or phenytoinSinus bradycardiaSinoatrial blockSecond- or third-degree atrioventricular blockAdams-Stokes syndrome
| Precautions | Risk of neurotoxicity at high doses or rapid infusion, Can worsen seizure control in some epilepsy syndromes, Monitor liver function due to CYP metabolism, May cause dizziness, ataxia, and cognitive impairment |
| Food/Dietary | No specific food interactions, but alcohol consumption increases risk of gastrointestinal bleeding. Maintain adequate hydration to reduce renal toxicity. |
| Clinical Pearls | KAINAIR (ketorolac tromethamine) is an NSAID for short-term management of moderate to severe acute pain, not to exceed 5 days. Monitor renal function, especially in elderly, dehydrated, or on diuretics. Contraindicated in peptic ulcer disease, bleeding disorders, and renal impairment. Use lowest effective dose; co-administration with other NSAIDs or aspirin increases bleeding risk. Intramuscular injection: give deeply; do not use epidural or intrathecal route due to neurotoxicity. |
| Patient Advice | Take this medication exactly as prescribed for the shortest duration necessary, usually no more than 5 days. · Avoid taking other NSAIDs (e.g., ibuprofen, naproxen) or aspirin while using this drug. · Report any signs of gastrointestinal bleeding (black stools, vomiting blood), easy bruising, or kidney problems (changes in urination, swelling) immediately. · This drug may cause dizziness or drowsiness; avoid driving or operating machinery until you know how it affects you. · Do not drink alcohol while taking this medication, as it increases the risk of stomach bleeding. · If you are pregnant, especially in the third trimester, do not use; avoid if breastfeeding. |
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