Table 5.
Studies evaluating morphine in cats
| Type of study | Dose and route* | Assessment | Results | Reference |
|---|---|---|---|---|
| Case report | MOR 0.06 mg/kg + BUPI 0.33 mg/kg in 0.13 ml/kg SAL intrathecal | Clinical | Within minutes of injection, a decrease in heart rate (from 150 to 110 bpm) and hypotension (MAP 60 mmHg) were recorded and resolved with the administration of 0.01 mg/kg glycopyrrolate and 10 ml/kg Ringer’s solution | 105 |
| Case report | MOR 0.43 mg in 0.86 ml SAL EPI | Clinical | Cat showed chronic urinary retention, constipation and decreased perineal reflex | 106 |
| Experimental | MOR 0.5 mg/kg IM, HYDRO 0.05–0.1– 0.2 mg/kg IM, B 0.02 mg/kg IM, BUT 0.2 mg/kg IM |
Body temperature measured with a thermistor | All treatments caused an increase in body temperature in comparison with baseline values | 40 |
| Experimental | MOR 0.1 mg/kg EPI, T 1 mg/kg EPI, SAL 0.22 ml/kg EPI |
SDS VAS Tail clamp test |
T group had a higher SDS and VAS score when compared with MOR at 8, 10 and 12 h postepidural. SAL group had a higher SDS and VAS score at all time points when compared with T and MOR groups. Euphoria was observed in five cats from MOR group and four from T group, and persisted up to 12 h postepidural | 107 |
| Experimental | MOR 100 μg/kg EPI, B 12.5 μg/kg EPI, SAL EPI |
TNT | TNT increased from 1–16 h in MOR group and from 1–10 h in B group in comparison with SAL | 71 |
| Experimental | MOR 0.2 mg/kg SC | TNT MNT |
TNT significantly increased from 45–60 mins, while MNT increased at 45–60 mins and 3–5 h after MOR administration | 32 |
| Experimental | MOR 0.2 mg/kg IM | TNT | TNT increased from 4 and 6 h, and euphoria was observed for 2–3 h after MOR administration. Mild sedation | 34 |
| Clinical | MOR EPI, MOR + BUPI EPI |
Mean dose ± SEM of MOR and MOR + BUPI was 0.16 ± 0.02 mg/kg and 1.16 ± 0.14 mg/kg, respectively. Two cats had urine retention | 108 | |
| Experimental | MOR 0.1 mg/kg IV, MOR 1 mg/kg IV |
MAC determination by tail clamp technique | Maximal MAC reductions were 28 ± 9% and 12 ± 4% with the lowest and highest doses of MOR, respectively. MOR 1 mg/kg IV provided clinically relevant isoflurane MAC reduction | 16 |
| Clinical: various surgeries or invasive diagnostic investigations | B 0.01 mg/kg IM, MOR 0.1 mg/kg IM |
VAS | B provided better postoperative analgesia than MOR at 60, 120 and 180 mins postanaesthesia. Rescue analgesia was necessary in 5/14 and 3/18 cats in MOR and B groups, respectively |
77 |
| Experimental | MOR 0.2 mg/kg IV and IM | PK | IV: mean ± SD T½ el = 76.3 ± 17.6 mins Clp = 24.1 ± 10.3 ml/kg/min Vdss = 2.6 ± 1.3 l/kg IM: mean ± SD T½ el = 93.6 ± 7.5 mins Clp = 13.9 ± 4 ml/kg/min Vdss= 1.7 ± 0.8 l/kg |
52 |
*
See footnote to Table 1
B = buprenorphine; bpm = beats per minute; BUPI = bupivacaine; BUT = butorphanol; Clp = plasma clearance; EPI = epidural; HYDRO = hydromorphone; MAC = minimum alveolar concentration; MAP = mean arterial pressure; MNT = mechanical nociceptive threshold; MOR = morphine; PK = pharmacokinetics; SAL = saline; SDS = simple descriptive scale; T = tramadol; T½ el = elimination half-life; TNT = thermal nociceptive threshold; VAS = visual analogue scale; Vdss = volume of distribution at steady state