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Samuel W Wilkinson,1 Emilie L Ungricht,1,2 William B West,1,2 Jacob T Harris,1,2 Brian Zaugg,1 Randall J Olson,1 Jeff H Pettey1 1Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA; 2University of Utah School of Medicine, Salt Lake City, UT, USACorrespondence: Jeff H Pettey, John A. Moran Eye Center, University of Utah, 65 Mario Capecchi Drive, Salt Lake City, UT, 84132, USA, Tel +1 801-581-2352, Fax +1 801-581-3357, Email jeff.pettey@hsc.utah.eduPurpose: To determine the difference, if any, in grooving efficiency at various settings on the Whitestar Signature Pro phacoemulsification (phaco) system.Methods: Cataractous lenses were simulated by exposing porcine lenses to formalin for 2 hours. A total of 120 lenses were analyzed at various power settings on both longitudinal and transversal handpieces. Twenty trials each were performed with power set to 25%, 50%, and 75% on both handpieces. A Whitestar Phaco Handpiece System was used to provide longitudinal power, and a Whitestar Signature Ellipsis Handpiece provided transversal power. Lenses were placed within a plastic chamber and grooved by an investigator blinded to settings. A second investigator recorded times and adjusted settings. The Whitestar Signature Pro phaco system was used for grooving.Results: There was no significant difference in grooving times between the longitudinal and transverse handpieces at any power setting (P > 0.05). There was a significant decrease in grooving times when comparing the 25% power setting with the 75% power setting for the transversal handpiece (P=0.021).Conclusion: Both longitudinal and transversal handpieces on the Whitestar Signature Pro phaco system produce similar results to one another at each power setting. There is a general trend toward shorter grooving times, reflecting greater efficiency, at higher power settings. Grooving efficiency on the transversal handpiece may be more affected by changes in the power settings as compared with the longitudinal settings.Keywords: phacoemulsification, cataract, phacoemulsification energy, transversal ultrasound, phacoemulsification efficiency

We report an unusual presentation of presumed mitomycin C toxicity with possible subsequent hypersensitization to other medication toxicities. A 50-year-old female presented three months after photorefractive keratectomy with intraoperative mitomycin C for the management of persistent epithelial defects, corneal haze, and edema. She was found to have used an expansive and rapidly changing medical regimen which may have caused additional toxicity. These medications included besifloxacin, bromfenac, and ketotifen. Additives such as benzalkonium chloride and DuraSite® may have also contributed. Intraoperative mitomycin C can result in longstanding corneal haze, edema, and delayed epithelial healing in the setting of corneal refractive surgery. These may leave the cornea more susceptible to additional subsequent medication toxicities during the postoperative period. This report describes a case of mitomycin C exposure leading to a prolonged sensitivity to other medication toxicities, which has not been discussed elsewhere in the literature.

Majid Moshirfar,1– 3 James Ellis,4 Daniel Beesley,5 Shannon E McCabe,1,6 Adam Lewis,7 William B West Jnr,4 Yasmyne Ronquillo,1 Phillip Hoopes Snr1 1Hoopes Vision Research Center, Hoopes Vision, Draper, UT, USA; 2John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, UT, USA; 3Utah Lions Eye Bank, Murray, UT, USA; 4University of Utah School of Medicine, Salt Lake City, UT, USA; 5Brigham Young University, Provo, UT, USA; 6Mission Hills Eye Center, Pleasant Hill, CA, USA; 7Kansas City University College of Osteopathic Medicine, Kansas City, MO, USACorrespondence: Majid MoshirfarHoopes Vision Research Center, Hoopes Vision, Draper, UT, USATel +1 801-568-0200Fax +1 801-563-0200Email cornea2020@me.comPurpose: To compare the visual performance of the AcrySof IQ PanOptix trifocal intraocular lens and the TECNIS Symfony extended depth-of-focus lens at near and distance visual ranges.Methods: A total of 146 patients (221 eyes) who underwent phacoemulsification and cataract extraction and received either a PanOptix or Symfony lens from January 2019 to July 2020 were included in the study (83 PanOptix non-toric, 30 PanOptix toric, 70 Symfony non-toric, and 38 Symfony toric). Uncorrected distance (UDVA), uncorrected near (UNVA), and corrected distance (CDVA) visual acuity were assessed at one-day, one-month, and three-months postoperatively. Averages of UDVA, UNVA, and CDVA were taken to evaluate which lens was superior at near and distance visual ranges. Secondary outcome measures including glare, halo, dryness, and problems with night vision were documented at each postoperative visit.Results: At one month postoperatively, the average UNVA was 0.16 ± 0.14 logMAR in the PanOptix group and 0.21 ± 0.14 logMAR in the Symfony group (P=0.007); the average UDVA for the PanOptix group was 0.09 ± 0.13 logMAR compared to the Symfony group at 0.10 ± 0.14 logMAR (P=0.67); and the average CDVA was 0.02 ± 0.05 logMAR in the PanOptix group and 0.00 ± 0.04 logMAR in the Symfony group (P=0.11). At three months postoperatively, there were no statistically significant differences in UNVA, UDVA, or CDVA between the two groups (P=0.18, 0.79, 0.68 respectively). There was no statistically significant difference in secondary outcome measures at one- and three-months (P=0.49, 0.10 respectively).Conclusion: The AcrySof IQ PanOptix trifocal intraocular lens appears to afford better UNVA compared to the TECNIS Symfony extended depth-of-focus intraocular lens at one-month postoperatively, though this difference was not seen at three months postoperatively. There is no statistically significant difference in UDVA and CDVA between the two groups at postoperative day one, one-month, and three-months.Keywords: visual acuity, intraocular lens, trifocal lens, extended depth-of-focus lens

PURPOSE: To report the 5-year occurrence, management, and outcomes of 12 eyes diagnosed as having central toxic keratopathy (CTK) after femtosecond laser–assisted in situ keratomileusis (FS-LASIK). METHODS: A retrospective chart review was conducted on 20,622 FS-LASIK procedures performed at a single site from January 2015 to December 2019 to identify patients diagnosed as having central toxic keratopathy. Preoperative and postoperative visual acuity, refraction, and imaging were recorded and analyzed. RESULTS: CTK occurred in 12 eyes of 8 patients after FSLASIK. A total of 75% of eyes were diagnosed during an outbreak that happened over 2 months and the remaining 25% were considered sporadic. Five eyes were treated with flap lift and irrigation and 7 eyes were treated non-surgically. The average time to resolution of CTK in eyes that underwent flap lift and irrigation was 53 days compared to 33 days in eyes treated non-surgically. All 5 eyes treated with flap lift and irrigation ultimately achieved uncorrected distance visual acuity of 0.1 logMAR or better, whereas only 3 of 7 eyes treated non-surgically achieved the same. At the final postoperative visit, the eyes treated with flap lift and irrigation measured on average 14 µm thinner and 1.60 diopters (D) flatter than the expected postoperative pachymetry and keratometry, respectively. Those treated non-surgically were on average 28 µm thinner and 1.70 D flatter than expected. CONCLUSIONS: CTK is a rare complication of FS-LASIK but can occur in clusters. Although management of CTK is debated, flap lift and irrigation may lead to better visual acuity and refractive and anatomic outcomes in some cases. [ J Refract Surg . 2021;37(1):25–31.]

Purpose To report the outcomes of sequential posterior chamber phakic intraocular lens (PC-pIOL) with corneal refractive surgery in conventional (PC-pIOL prior to refractive surgery) and reverse (refractive surgery prior to PC-pIOL) bioptics for treating high myopic astigmatism. Setting Tertiary refractive center, Draper, Utah, USA. Design Retrospective case series. Methods Medical records of patients who underwent planned bioptics were reviewed. Surgery involved PC-pIOL placement using an implantable collamer lens (ICL) with preceding or subsequent LASIK or PRK. Pre- and postoperative manifest spherical equivalent (SEQ), visual acuity, and PC-pIOL vault were analyzed. Results Of the 51 eyes present at 12 months postoperatively, 49 eyes (96%) achieved target SEQ within ±1.00 D and an identical amount achieved refractive astigmatism ≤1.00 D. Post-bioptics eyes achieved a postoperative UDVA equal to or better than preoperative CDVA in 45 eyes (88%). Efficacy and safety indices were 1.08 ± 0.20 (41 eyes) and 1.13 ± 0.22 (44 eyes) for conventional bioptics and 0.99 ± 0.42 (7 eyes) and 1.15 ± 0.38 (7 eyes) for reverse bioptics eyes at 12 months. The maximum PC-pIOL vault of conventional bioptics eyes (27 eyes) within 6 months before and after LASIK/PRK was 385 ± 159 μm and 377 ± 135 μm, respectively (P = 0.71). Conclusion Bioptics for high myopic astigmatism was safe and effective. Reverse bioptics, although not as traditional, could provide similar results. Additionally, the PC-pIOL vault does not appear to be affected by LASIK/PRK.

Introduction Enhanced recovery protocols include multimodal perioperative pain control and frequently include use of NSAIDs. There is conflicting evidence that ketorolac use in inflammatory bowel disease (IBD) may precipitate disease flares and postoperative complications. The outcomes of children who receive ketorolac in this setting are not well known. We sought to evaluate ketorolac utilization in children following colectomy for ulcerative colitis. Methods All patients undergoing colectomy for ulcerative colitis between 2007 and 2017 at a tertiary children's hospital were reviewed. We collected patient age, duration of symptoms, operative details, medication utilization, length of stay, and postoperative complications. We performed a cohort comparison of these variables across patients who did vs. did not receive postoperative ketorolac. Results Sixty children were identified with median age at diagnosis of 12.6 years (IQR: 9.9–14.5). At colectomy, patients had a median PUCAI score of 60 (45–70), ESR 34 mm/h (15–50), hemoglobin 10.9 g/dL (9.3–12.9), and albumin 3.1 g/dL (2.4–3.8). Postoperatively, 45% (n = 27) received ketorolac. Patients in both cohorts had a similar length of stay, duration of opioid exposure, total morphine equivalents utilized, readmission rate, and unexpected return to the operating room. There were no documented cases of postoperative bleeding, acute kidney injury, or disease related flares among children receiving ketorolac. Conclusions Administration of ketorolac after colectomy in IBD was not associated with an increase in any postoperative complications, though the study was underpowered to detect these differences. However, ketorolac administration did not lead to a decreased utilization of opioid analgesia. Further prospective research is necessary to understand whether ketorolac in this population is safe and offers benefit. Type of study Retrospective study. Level of evidence III

Majid Moshirfar,1– 3 Andrew C Thomson,4 William B West Jr,5 MacGregor N Hall,4 Shannon E McCabe,1 Robert J Thomson,4 Yasmyne C Ronquillo,1 Phillip C Hoopes1 1Hoopes Vision Research Center, Hoopes Vision, Draper, UT, USA; 2John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA; 3Utah Lions Eye Bank, Murray, UT, USA; 4McGovern Medical School at the University of Texas Health Science Center at Houston, Houston, TX, USA; 5University of Utah School of Medicine, Salt Lake City, UT, USACorrespondence: Majid MoshirfarHoopes Vision Research Center, 11820 S. State Street Suite #200, Draper, UT 84020, USATel +1 801-568-0200Fax +1 801-563-0200Email cornea2020@me.comPurpose: To assess a single site’s initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes and vector analysis results with the US Food and Drug Administration (FDA) results and published literature.Patients and Methods: Forty-eight eyes (29 patients) with mean preoperative sphere of − 5.11 ± 1.31 diopters (D) and cylinder of − 1.12 ± 0.60 D underwent SMILE. Visual acuity, refractive, and vector analysis outcomes as well as subjective measures were reported at three and twelve months postoperatively and compared with FDA results and the published literature between 2014 and 2020 involving treatment of patients with mean cylinders of >− 0.50 to ≤− 3.00 D.Results: At three and twelve months, 43 and 32 eyes were evaluated, respectively. At twelve months, mean cylinder power was reduced to − 0.38 ± 0.38 D with 78.1% achieving ≤± 0.50 D. Uncorrected distance visual acuity (UDVA) ≥ 20/20 was achieved in 77.4% of eyes by twelve months with 100% achieving ≥ 20/30 UDVA. No loss of corrected distance visual acuity was observed in eyes seen at twelve months. Correction index (CI) at twelve months was 0.90 indicating overall undercorrection of 10%. Twelve-month CI was 0.96, 0.90, and 0.83 in eyes with preoperative cylinders of

Previous studies have demonstrated safety and efficacy using 6.0 and 6.5 mm optical zones in the WaveLight EX500 Excimer Laser System but have not evaluated if differing optical zone sizes influence refractive outcomes. This study examines visual outcomes between two study populations undergoing LASIK with either a 6.0 mm (1332 patients) or 6.5 mm (1332 patients) optical zone. Outcomes were further stratified by severity of myopia (low, moderate, and high) and astigmatism (low and high). Patients were matched by age and preoperative manifest sphere and cylinder. Postoperative measurements were then compared. The 6.5 mm group demonstrated better postoperative manifest refractive spherical equivalent (MRSE), manifest sphere, and absolute value of the difference in actual and target spherical equivalent refraction (|∆ SEQ|), within the total population, moderate myopia, and low astigmatism groups, but this did not lead to improved postoperative uncorrected distance visual acuity (UDVA) or best corrected distance visual acuity (CDVA). Though astigmatic correction and postoperative angle of error were similar between optical zone sizes, they were significantly worse with high myopia. Overall, this study demonstrates differences in visual outcomes between the 6.0 and 6.5 mm optical zone sizes that may warrant consideration, however, essentially, the results are comparable between them.

Although the use of femtosecond lasers instead of mechanical devices has decreased the incidence of flap complications following laser-assisted in situ keratomileusis (LASIK), dislocations and striae still occur. Flap repositioning is an effective intervention to improve visual outcomes after acute flap complications in both microkeratome-assisted and femtosecond-assisted LASIK. This retrospective case series included patients undergoing flap repositioning secondary to acute flap dislocation and/or visually significant striae within the first two weeks following femtosecond LASIK (FS-LASIK) from 2015 to 2020 at a single institution. Preoperative, intraoperative, and postoperative de-identified data were analyzed for incidence, risk factors, and visual acuity outcomes. The incidence of flap repositioning was 0.35% in 21,536 eyes (n = 70). Indications for repositioning included acute flap dislocation (35.7%) and visually significant striae (64.3%). High myopia (OR = 3.04, p = 0.001) and patient age over 50 years (OR = 3.69, p = 0.001) were the strongest risk factors for these complications. Prior to flap repositioning, uncorrected distance visual acuity (UDVA) of 20/20 or better and 20/40 or better occurred in 19% and 57% of eyes, respectively. After repositioning, a final UDVA of 20/20 or better and 20/40 or better occurred in 78% and 98% of eyes, respectively. After repositioning, one line of UDVA was lost in two eyes (2.8%) and two lines were lost in one eye (1.4%). Risk factors for acute flap dislocation included high myopia and age over 50 years. Flap repositioning was effective in salvaging visual outcomes.

Introduction Laser-assisted in-situ keratomileusis (LASIK) for the correction of hyperopia and hyperopic astigmatism is challenging and has been less studied than for the correction of myopia and myopic astigmatism. The aim of this study was to analyze the refractive outcomes of LASIK in hyperopia and hyperopic astigmatic eyes using a wave-front optimized laser platform (the Allegretto EX500 laser) and perform a historical comparison with other excimer lasers within the past two decades. Methods A one-center (Tertiary Refractive Center, Draper, Utah), retrospective, non-comparative study was conducted on 379 eyes treated with LASIK for hyperopia and hyperopic astigmatism. The data retrieved on these eyes were analyzed using uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and spherical equivalents. A literature search of excimer platforms in use in the past 20 years and a comparison of US Federal Drug Administration-approved platforms for hyperopia were performed. Results At 3 and 12 months postoperatively, 142 (66%) and 81 (69%) eyes had a UDVA of 20/20 or better and 207 (96%) and 114 (97%) eyes had a UDVA of 20/40 or better, respectively. The mean refractive spherical equivalent was − 0.52 ± 0.78 D at 3 months and − 0.46 ± 0.79 D at 12 months. At 12 months, 181 (96%) eyes achieved a spherical equivalent within ± 1.00 D of the intended target. Studies published before 2005 reported lower rates of UDVA 20/20 or better (32%) compared to those published after (68%); however, this discrepancy was less evident for UDVA 20/40 or better. A similar trend towards improved accuracy was noted in the literature with postoperative manifest refractive spherical equivalent within ± 0.50 D before and after 2005. Conclusion There has been significant improvement in safety, efficacy, stability, and accuracy of LASIK treatment for hyperopia and hyperopic astigmatism within the past two decades. Newer excimer lasers meet industry standards and in particular, the Allegretto EX500 used in this study exceeded industry standards.

Key Points Question Do International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes accurately capture presenting symptoms of fever, cough, and dyspnea among patients being tested for coronavirus disease 2019 (COVID-19)? Findings In this cohort study, an electronic medical record review of 2201 patients tested for COVID-19 between March 10 and April 6, 2020, found that ICD-10 codes had poor sensitivity and negative predictive value for capturing fever, cough, and dyspnea. Meaning These findings suggest that symptom-specific ICD-10 codes do not accurately capture COVID-19–related symptoms and should not be used to populate symptoms in electronic medical record–based cohorts., This cohort study compares the performance of International Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes specific for fever, cough, and dyspnea with electronic medical record review for patients tested for coronavirus disease 2019 (COVID-19)., Importance International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes are used to characterize coronavirus disease 2019 (COVID-19)–related symptoms. Their accuracy is unknown, which could affect downstream analyses. Objective To compare the performance of fever-, cough-, and dyspnea-specific ICD-10 codes with medical record review among patients tested for COVID-19. Design, Setting, and Participants This cohort study included patients who underwent quantitative reverse transcriptase–polymerase chain reaction testing for severe acute respiratory syndrome coronavirus 2 at University of Utah Health from March 10 to April 6, 2020. Data analysis was performed in April 2020. Main Outcomes and Measures The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ICD-10 codes for fever (R50*), cough (R05*), and dyspnea (R06.0*) were compared with manual medical record review. Performance was calculated overall and stratified by COVID-19 test result, sex, age group (64 years), and inpatient status. Bootstrapping was used to generate 95% CIs, and Pearson χ2 tests were used to compare different subgroups. Results Among 2201 patients tested for COVD-19, the mean (SD) age was 42 (17) years; 1201 (55%) were female, 1569 (71%) were White, and 282 (13%) were Hispanic or Latino. The prevalence of fever was 66% (1444 patients), that of cough was 88% (1930 patients), and that of dyspnea was 64% (1399 patients). For fever, the sensitivity of ICD-10 codes was 0.26 (95% CI, 0.24-0.29), specificity was 0.98 (95% CI, 0.96-0.99), PPV was 0.96 (95% CI, 0.93-0.97), and NPV was 0.41 (95% CI, 0.39-0.43). For cough, the sensitivity of ICD-10 codes was 0.44 (95% CI, 0.42-0.46), specificity was 0.88 (95% CI, 0.84-0.92), PPV was 0.96 (95% CI, 0.95-0.97), and NPV was 0.18 (95% CI, 0.16-0.20). For dyspnea, the sensitivity of ICD-10 codes was 0.24 (95% CI, 0.22-0.26), specificity was 0.97 (95% CI, 0.96-0.98), PPV was 0.93 (95% CI, 0.90-0.96), and NPV was 0.42 (95% CI, 0.40-0.44). ICD-10 code performance was better for inpatients than for outpatients for fever (χ2 = 41.30; P

Femtosecond (FS) lasers initially had a higher incidence of diffuse lamellar keratitis (DLK) compared with microkeratome flap creation. It has been theorized that higher-frequency lower-energy (HFLE) FS lasers would reduce the incidence of DLK. Our study sought to evaluate the incidence of newer HFLE FS lasers with pulse frequencies above 60 kHz. It was a retrospective case-control study evaluating the incidence of DLK following flap creation with one of three FS lasers (AMO iFs, WaveLight FS200, Zeiss VisuMax). Uncomplicated LASIK cases were included as the control group (14,348 eyes) and cases of DLK were recorded in the study group (637 eyes). Of the 637 cases of DLK, 76 developed stage II, 25 progressed to stage III, and only three developed stage IV DLK. The overall incidence rate of DLK was 4.3%, it has fallen with the invention of newer HFLE FS lasers and is approaching the DLK incidence rates of DLK with microkeratome.

Activation of dopaminergic (DA) systems is a necessary component of the behavior effects of d -amphetamine, but other neurotransmitters such as norepinephrine (NE) and serotonin (5-HT) appear to modulate DA input; thus, they might have an important role in the stimulus (subjective) effects of this drug. Therefore, rats were trained to discriminate d -amphetamine (1 mg/kg) from saline and given combination (antagonism, potentiation) or substitution (generalization) tests with drugs that act through DA, noradrenergic, or serotonergic (5-HT) mechanisms. In the first of two experiments, the D 1 antagonist SCH 39166 blocked the effects of d -amphetamine (1 mg/kg) at doses of 0.05, 0.1, and 0.2 mg/kg. NE and 5-HT antagonists including prazosin (0.5–2 mg/kg), idazoxan (1.25–5 mg/kg), ketanserin (0.06–0.15 mg/kg), and metergoline (5–20 mg/kg) had no significant effects on the d -amphetamine cue. In the second experiment, neither the α 2 -NE agonist clonidine (0.0025–0.1 mg/kg), the β-NE agonist salbutamol (0.05–0.25 mg/kg), nor the NE uptake inhibitor nisoxetine (5–15 mg/kg) had d -amphetamine-like effects. The α 2 -NE antagonist yohimbine (0.5–2 mg/kg) and the β-NE antagonist propranolol (0.5–3 mg/kg) failed to alter the d -amphetamine cue. ICS 205–930 (10 mg/kg) neither mimicked nor blocked the effects of 1 mg/kg of d -amphetamine. Indeed, this 5-HT 3 antagonist potentiated the actions of lower doses of d -amphetamine (0.25–0.4 mg/kg); the potentiation of the 0.25-mg/kg dose was blocked significantly by the α 1 -NE antagonist prazosin (1 mg/kg). These results suggest that the discriminative stimulus effects of d -amphetamine are mediated primarily by DA neuronal systems and that these effects are similar to those of drugs that act through 5-HT 3 receptors; this similarity could be mediated by α 1 -NE mechanisms.

Research in our laboratory, supported by NIDA and facilitated by Roger Brown, has indicated that serotonergic neuronal systems are involved in the discriminative stimulus effects of LSD. However, the only compounds that fully antagonize the LSD cue act at both serotonin (5-HT) and dopamine (DA) receptors. In addition, substitution for LSD in standard drug vs. no-drug (DND) discriminations does not necessarily predict either similar mechanisms of action or hallucinogenic potency because 'false positives' occur when animals are given drugs such as lisuride (LHM), quipazine, or, possibly, yohimbine. These effects can be greatly reduced by using drug vs. drug (D-D), drug vs. drug vs. no drug (D-ND), or drug vs. ' other' drug (saline, cocaine, pentobarbital) training procedures. Additional studies, in which drugs were administered directly into the cerebral ventricles or specific brain areas, suggest that structures containing terminal fields of serotonergic neurons might be involved in the stimulus effects of LSD.

Drugs such as PCP and MK-801 can cause psychotic reactions in humans by antagonizing NMDA receptors. This action is ultimately toxic to certain cortical neurons and may be one mechanism underlying neurodegenerative diseases, including schizophrenia. It has been reported that hallucinogens such as LSD, DOM, and DOI can block the neurotoxic effects of NMDA antagonists, possibly by activating inhibitory 5-HT2A receptors on GABAergic interneurons that normally inhibit glutamatergic projections to the retrosplenial and cingulate cortexes. The purpose of this experiment was to determine the extent to which similar drugs might also alter the behavioral effects of one NMDA antagonist, PCP. Rats were trained to discriminate this compound (2.5 mg/kg) from saline and were then given a series of antagonist tests. It was found that LSD (0.32 mg/kg) and DOM (4.0 mg/kg) blocked the PCP cue completely; DMT (8.0 mg/kg) and a structural congener of LSD, lisuride (LHM; 0.4 mg/kg), blocked the effects of PCP partially. The 5-HT/DA antagonists spiperone and ritanserin had no effect on the PCP cue. These data suggest that LSD, DOM, and, less effectively, DMT and LHM can block the behavioral as well as the neurotoxic effects of NMDA antagonists most likely through agonist actions at 5-HT2 receptors.

In an attempt to increase the selectivity of drug discrimination, rats were trained to discriminate LSD (0.08 mg/kg) from a group of "other" compounds consisting of cocaine (10 mg/kg), pentobarbital (5 mg/kg), and saline. Acquisition of this LSD-other discrimination was rapid (31 days) in chambers equipped with retractable levers and did not differ significantly from that of a group of animals trained to discriminate LSD from saline (26 days). In substitution (generalization) tests, hallucinogens such as LSD, DMT, and DOM mimicked LSD in a dose-dependent manner in both groups. The designer drug (+/-)MDMA substituted for LSD in the LSD-other group (ED50 = 1.38) but did not substitute for the training drug in the LSD-ND group; neither (+) MDMA nor PCP mimicked LSD in either group. Most importantly, lisuride, quipazine, and yohimbine, drugs that have been described as "false positives," substituted for LSD in animals trained to discriminate LSD from saline (ED50s = 0.012, 1.662, 2.344, respectively), but not in animals trained to discriminate LSD from other drugs. Thus, the LSD-other training procedure can be described as more selective than the standard drug-ND procedure.