Table 2.

General scientometric data on topics related to pain modulators and their molecular targets

Number	Topic	Initial 5-year perioda	Number of articles			Number of patents			Drugs approved by FDA for pain relief
			2004–2008	2009–2013	Total of all 5-year periods	2004–2008	2009–2013	Total of all 5-year periods
1	Purinergic receptors	1984–1988	549	1,120	2,354	14	0	39
2	Serotonin	1984–1988	1,608	1,555	6,241	21	11	135	Sumatriptan (92), zolmitriptan (97), naratriptan (98), rizatriptan (98), almotriptan (01), frovatriptan (01), eletriptan (02), duloxetine (06), milnacipran (09)
3	Bradykinin	1989–1993	252	208	943	9	11	42
4	Substance P	1989–1993	514	481	2,097	3	1	35
5	TRP channels	1989–1993	1,187	1,722	4,000	17	14	60	Capsaicin, 8% patch (09)
6	Calcium channels	1994–1998	595	777	1,722	29	10	76	Ziconotide (04)
7	Cholecystokinin	1994–1998	108	79	438	1	0	2
8	Cytokines	1994–1998	2,066	3,410	7,186	11	2	33
9	GABA	1994–1998	1,335	1,945	4,263	5	8	30	Gabapentin (02), pregabalin (09), gabapentin enacarbil (12), valproate (14)
10	Glutamate	1994–1998	1,517	1,532	4,489	26	21	130	Ketamine (confirmed in CR, 06)b
11	Botulinum toxins	1999–2003	505	622	1,389	22	13	65
12	Cannabinoids	1999–2003	557	651	1,473	18	17	48	Dronabinol (confirmed in CR, 07)b
13	CGRP	1999–2003	526	760	1,589	54	31	88
14	Neurotrophins	1999–2003	426	674	1,405	15	13	30
15	Nitric oxide synthase	1999–2003	329	462	1,040	11	5	36
16	Protein kinases	1999–2003	869	1,525	2,773	5	12	27
17	VGSC	2004–2008	267	422	689	7	9	16

Notes:

^aPeriod when the number of articles and patents were ≥300 or ≥3, respectively;

^beffectiveness in pain confirmed by meta-analysis, see in Bell et al21 and Iskedjian et al.28

Abbreviations: TRP, transient receptor potential; GABA, gamma aminobutyric acid; CGRP, calcitonin gene-related peptide; FDA, US Food and Drug Administration; VGSC, voltage-gated sodium channels; CR, Cochrane review.